diff --git a/cpp/ql/lib/semmle/code/cpp/controlflow/IRGuards.qll b/cpp/ql/lib/semmle/code/cpp/controlflow/IRGuards.qll
index bcd214ec0000..83f8dc8b3bc7 100644
--- a/cpp/ql/lib/semmle/code/cpp/controlflow/IRGuards.qll
+++ b/cpp/ql/lib/semmle/code/cpp/controlflow/IRGuards.qll
@@ -790,6 +790,27 @@ private predicate simple_comparison_eq(Instruction test, Operand op, int k, Abst
     exists(switch.getSuccessor(case)) and
     case.getValue().toInt() = k
   )
+  or
+  // There's no implicit CompareInstruction in files compiled as C since C
+  // doesn't have implicit boolean conversions. So instead we check whether
+  // there's a branch on a value of pointer or integer type.
+  exists(ConditionalBranchInstruction branch, IRType type |
+    not test instanceof CompareInstruction and
+    type = test.getResultIRType() and
+    (type instanceof IRAddressType or type instanceof IRIntegerType) and
+    test = branch.getCondition() and
+    op.getDef() = test
+  |
+    // We'd like to also include a case such as:
+    // ```
+    // k = 1 and
+    // value.(BooleanValue).getValue() = true
+    // ```
+    // but all we know is that the value is non-zero in the true branch.
+    // So we can only conclude something in the false branch.
+    k = 0 and
+    value.(BooleanValue).getValue() = false
+  )
 }
 
 private predicate complex_eq(
diff --git a/cpp/ql/test/library-tests/controlflow/guards-ir/tests.expected b/cpp/ql/test/library-tests/controlflow/guards-ir/tests.expected
index 943d7028a5d2..d50ca1609163 100644
--- a/cpp/ql/test/library-tests/controlflow/guards-ir/tests.expected
+++ b/cpp/ql/test/library-tests/controlflow/guards-ir/tests.expected
@@ -148,6 +148,24 @@ astGuardsCompare
 | 109 | y < 0+0 when ... < ... is true |
 | 109 | y >= 0+0 when ... < ... is false |
 | 109 | y >= 0+0 when ... \|\| ... is false |
+| 126 | 1 != 0 when 1 is true |
+| 126 | 1 != 0 when ... && ... is true |
+| 126 | 1 == 0 when 1 is false |
+| 126 | call to test3_condition != 0 when ... && ... is true |
+| 126 | call to test3_condition != 0 when call to test3_condition is true |
+| 126 | call to test3_condition == 0 when call to test3_condition is false |
+| 131 | b != 0 when b is true |
+| 131 | b == 0 when b is false |
+| 137 | 0 != 0 when 0 is true |
+| 137 | 0 == 0 when 0 is false |
+| 146 | ! ... != 0 when ! ... is true |
+| 146 | ! ... == 0 when ! ... is false |
+| 152 | x != 0 when ... && ... is true |
+| 152 | x != 0 when x is true |
+| 152 | x == 0 when x is false |
+| 152 | y != 0 when ... && ... is true |
+| 152 | y != 0 when y is true |
+| 152 | y == 0 when y is false |
 | 156 | ... + ... != x+0 when ... == ... is false |
 | 156 | ... + ... == x+0 when ... == ... is true |
 | 156 | x != ... + ...+0 when ... == ... is false |
@@ -186,6 +204,8 @@ astGuardsCompare
 | 175 | call to foo != 0+0 when ... == ... is false |
 | 175 | call to foo == 0 when ... == ... is true |
 | 175 | call to foo == 0+0 when ... == ... is true |
+| 181 | x != 0 when x is true |
+| 181 | x == 0 when x is false |
 astGuardsControl
 | test.c:7:9:7:13 | ... > ... | false | 10 | 11 |
 | test.c:7:9:7:13 | ... > ... | true | 7 | 9 |
@@ -487,8 +507,27 @@ astGuardsEnsure_const
 | test.c:109:9:109:14 | ... == ... | test.c:109:9:109:9 | x | != | 0 | 109 | 109 |
 | test.c:109:9:109:14 | ... == ... | test.c:109:9:109:9 | x | != | 0 | 113 | 113 |
 | test.c:109:9:109:23 | ... \|\| ... | test.c:109:9:109:9 | x | != | 0 | 113 | 113 |
+| test.c:126:7:126:7 | 1 | test.c:126:7:126:7 | 1 | != | 0 | 126 | 126 |
+| test.c:126:7:126:7 | 1 | test.c:126:7:126:7 | 1 | != | 0 | 126 | 128 |
+| test.c:126:7:126:7 | 1 | test.c:126:7:126:7 | 1 | != | 0 | 131 | 131 |
+| test.c:126:7:126:7 | 1 | test.c:126:7:126:7 | 1 | != | 0 | 131 | 132 |
+| test.c:126:7:126:7 | 1 | test.c:126:7:126:7 | 1 | != | 0 | 134 | 123 |
+| test.c:126:7:126:28 | ... && ... | test.c:126:7:126:7 | 1 | != | 0 | 126 | 128 |
+| test.c:126:7:126:28 | ... && ... | test.c:126:12:126:26 | call to test3_condition | != | 0 | 126 | 128 |
+| test.c:126:12:126:26 | call to test3_condition | test.c:126:12:126:26 | call to test3_condition | != | 0 | 126 | 128 |
+| test.c:131:7:131:7 | b | test.c:131:7:131:7 | b | != | 0 | 131 | 132 |
+| test.c:137:7:137:7 | 0 | test.c:137:7:137:7 | 0 | == | 0 | 142 | 136 |
+| test.c:146:7:146:8 | ! ... | test.c:146:7:146:8 | ! ... | != | 0 | 146 | 147 |
+| test.c:152:10:152:10 | x | test.c:152:10:152:10 | x | != | 0 | 151 | 152 |
+| test.c:152:10:152:10 | x | test.c:152:10:152:10 | x | != | 0 | 152 | 152 |
+| test.c:152:10:152:15 | ... && ... | test.c:152:10:152:10 | x | != | 0 | 151 | 152 |
+| test.c:152:10:152:15 | ... && ... | test.c:152:15:152:15 | y | != | 0 | 151 | 152 |
+| test.c:152:15:152:15 | y | test.c:152:15:152:15 | y | != | 0 | 151 | 152 |
 | test.c:175:13:175:32 | ... == ... | test.c:175:13:175:15 | call to foo | != | 0 | 175 | 175 |
 | test.c:175:13:175:32 | ... == ... | test.c:175:13:175:15 | call to foo | == | 0 | 175 | 175 |
+| test.c:181:9:181:9 | x | test.c:181:9:181:9 | x | != | 0 | 181 | 182 |
+| test.c:181:9:181:9 | x | test.c:181:9:181:9 | x | != | 0 | 186 | 180 |
+| test.c:181:9:181:9 | x | test.c:181:9:181:9 | x | == | 0 | 183 | 184 |
 | test.cpp:18:8:18:10 | call to get | test.cpp:18:8:18:10 | call to get | != | 0 | 19 | 19 |
 | test.cpp:31:7:31:13 | ... == ... | test.cpp:31:7:31:7 | x | != | -1 | 30 | 30 |
 | test.cpp:31:7:31:13 | ... == ... | test.cpp:31:7:31:7 | x | != | -1 | 34 | 34 |
@@ -640,6 +679,20 @@ irGuardsCompare
 | 109 | y < 0+0 when CompareLT: ... < ... is true |
 | 109 | y >= 0 when CompareLT: ... < ... is false |
 | 109 | y >= 0+0 when CompareLT: ... < ... is false |
+| 126 | 1 != 0 when Constant: 1 is true |
+| 126 | 1 == 0 when Constant: 1 is false |
+| 126 | call to test3_condition != 0 when Call: call to test3_condition is true |
+| 126 | call to test3_condition == 0 when Call: call to test3_condition is false |
+| 131 | b != 0 when Load: b is true |
+| 131 | b == 0 when Load: b is false |
+| 137 | 0 != 0 when Constant: 0 is true |
+| 137 | 0 == 0 when Constant: 0 is false |
+| 146 | ! ... != 0 when LogicalNot: ! ... is true |
+| 146 | ! ... == 0 when LogicalNot: ! ... is false |
+| 152 | x != 0 when Load: x is true |
+| 152 | x == 0 when Load: x is false |
+| 152 | y != 0 when Load: y is true |
+| 152 | y == 0 when Load: y is false |
 | 156 | ... + ... != x+0 when CompareEQ: ... == ... is false |
 | 156 | ... + ... == x+0 when CompareEQ: ... == ... is true |
 | 156 | x != ... + ...+0 when CompareEQ: ... == ... is false |
@@ -678,6 +731,8 @@ irGuardsCompare
 | 175 | call to foo != 0+0 when CompareEQ: ... == ... is false |
 | 175 | call to foo == 0 when CompareEQ: ... == ... is true |
 | 175 | call to foo == 0+0 when CompareEQ: ... == ... is true |
+| 181 | x != 0 when Load: x is true |
+| 181 | x == 0 when Load: x is false |
 irGuardsControl
 | test.c:7:9:7:13 | CompareGT: ... > ... | false | 11 | 11 |
 | test.c:7:9:7:13 | CompareGT: ... > ... | true | 8 | 8 |
@@ -999,8 +1054,21 @@ irGuardsEnsure_const
 | test.c:109:9:109:14 | CompareEQ: ... == ... | test.c:109:9:109:9 | Load: x | != | 0 | 109 | 109 |
 | test.c:109:9:109:14 | CompareEQ: ... == ... | test.c:109:9:109:9 | Load: x | != | 0 | 113 | 113 |
 | test.c:109:19:109:23 | CompareLT: ... < ... | test.c:109:19:109:19 | Load: y | >= | 0 | 113 | 113 |
+| test.c:126:7:126:7 | Constant: 1 | test.c:126:7:126:7 | Constant: 1 | != | 0 | 126 | 126 |
+| test.c:126:7:126:7 | Constant: 1 | test.c:126:7:126:7 | Constant: 1 | != | 0 | 127 | 127 |
+| test.c:126:7:126:7 | Constant: 1 | test.c:126:7:126:7 | Constant: 1 | != | 0 | 131 | 131 |
+| test.c:126:7:126:7 | Constant: 1 | test.c:126:7:126:7 | Constant: 1 | != | 0 | 132 | 132 |
+| test.c:126:7:126:7 | Constant: 1 | test.c:126:7:126:7 | Constant: 1 | != | 0 | 134 | 134 |
+| test.c:126:12:126:26 | Call: call to test3_condition | test.c:126:12:126:26 | Call: call to test3_condition | != | 0 | 127 | 127 |
+| test.c:131:7:131:7 | Load: b | test.c:131:7:131:7 | Load: b | != | 0 | 132 | 132 |
+| test.c:137:7:137:7 | Constant: 0 | test.c:137:7:137:7 | Constant: 0 | == | 0 | 142 | 142 |
+| test.c:146:7:146:8 | LogicalNot: ! ... | test.c:146:7:146:8 | LogicalNot: ! ... | != | 0 | 147 | 147 |
+| test.c:152:10:152:10 | Load: x | test.c:152:10:152:10 | Load: x | != | 0 | 152 | 152 |
+| test.c:152:15:152:15 | Load: y | test.c:152:15:152:15 | Load: y | != | 0 | 152 | 152 |
 | test.c:175:13:175:32 | CompareEQ: ... == ... | test.c:175:13:175:15 | Call: call to foo | != | 0 | 175 | 175 |
 | test.c:175:13:175:32 | CompareEQ: ... == ... | test.c:175:13:175:15 | Call: call to foo | == | 0 | 175 | 175 |
+| test.c:181:9:181:9 | Load: x | test.c:181:9:181:9 | Load: x | != | 0 | 182 | 182 |
+| test.c:181:9:181:9 | Load: x | test.c:181:9:181:9 | Load: x | == | 0 | 184 | 184 |
 | test.cpp:18:8:18:12 | CompareNE: (bool)... | test.cpp:18:8:18:10 | Call: call to get | != | 0 | 19 | 19 |
 | test.cpp:31:7:31:13 | CompareEQ: ... == ... | test.cpp:31:7:31:7 | Load: x | != | -1 | 34 | 34 |
 | test.cpp:31:7:31:13 | CompareEQ: ... == ... | test.cpp:31:7:31:7 | Load: x | == | -1 | 30 | 30 |
diff --git a/cpp/ql/test/library-tests/controlflow/guards/Guards.expected b/cpp/ql/test/library-tests/controlflow/guards/Guards.expected
index 08a8a9281bb1..13d6c2b654ff 100644
--- a/cpp/ql/test/library-tests/controlflow/guards/Guards.expected
+++ b/cpp/ql/test/library-tests/controlflow/guards/Guards.expected
@@ -26,6 +26,12 @@
 | test.c:137:7:137:7 | 0 |
 | test.c:146:7:146:8 | ! ... |
 | test.c:146:8:146:8 | x |
+| test.c:152:8:152:8 | p |
+| test.c:158:8:158:9 | ! ... |
+| test.c:158:9:158:9 | p |
+| test.c:164:8:164:8 | s |
+| test.c:170:8:170:9 | ! ... |
+| test.c:170:9:170:9 | s |
 | test.cpp:18:8:18:10 | call to get |
 | test.cpp:31:7:31:13 | ... == ... |
 | test.cpp:42:13:42:20 | call to getABool |
diff --git a/cpp/ql/test/library-tests/controlflow/guards/GuardsCompare.expected b/cpp/ql/test/library-tests/controlflow/guards/GuardsCompare.expected
index 756140604e13..a2f418b3d7bb 100644
--- a/cpp/ql/test/library-tests/controlflow/guards/GuardsCompare.expected
+++ b/cpp/ql/test/library-tests/controlflow/guards/GuardsCompare.expected
@@ -149,3 +149,23 @@
 | 111 | 0.0 == i+0 when ... != ... is false |
 | 111 | i != 0.0+0 when ... != ... is true |
 | 111 | i == 0.0+0 when ... != ... is false |
+| 126 | 1 != 0 when 1 is true |
+| 126 | 1 != 0 when ... && ... is true |
+| 126 | 1 == 0 when 1 is false |
+| 126 | call to test3_condition != 0 when ... && ... is true |
+| 126 | call to test3_condition != 0 when call to test3_condition is true |
+| 126 | call to test3_condition == 0 when call to test3_condition is false |
+| 131 | b != 0 when b is true |
+| 131 | b == 0 when b is false |
+| 137 | 0 != 0 when 0 is true |
+| 137 | 0 == 0 when 0 is false |
+| 146 | ! ... != 0 when ! ... is true |
+| 146 | ! ... == 0 when ! ... is false |
+| 152 | p != 0 when p is true |
+| 152 | p == 0 when p is false |
+| 158 | ! ... != 0 when ! ... is true |
+| 158 | ! ... == 0 when ! ... is false |
+| 164 | s != 0 when s is true |
+| 164 | s == 0 when s is false |
+| 170 | ! ... != 0 when ! ... is true |
+| 170 | ! ... == 0 when ! ... is false |
diff --git a/cpp/ql/test/library-tests/controlflow/guards/GuardsControl.expected b/cpp/ql/test/library-tests/controlflow/guards/GuardsControl.expected
index 62d9b0a12294..cf36a58a515b 100644
--- a/cpp/ql/test/library-tests/controlflow/guards/GuardsControl.expected
+++ b/cpp/ql/test/library-tests/controlflow/guards/GuardsControl.expected
@@ -79,6 +79,12 @@
 | test.c:137:7:137:7 | 0 | false | 142 | 136 |
 | test.c:146:7:146:8 | ! ... | true | 146 | 147 |
 | test.c:146:8:146:8 | x | false | 146 | 147 |
+| test.c:152:8:152:8 | p | true | 152 | 154 |
+| test.c:158:8:158:9 | ! ... | true | 158 | 160 |
+| test.c:158:9:158:9 | p | false | 158 | 160 |
+| test.c:164:8:164:8 | s | true | 164 | 166 |
+| test.c:170:8:170:9 | ! ... | true | 170 | 172 |
+| test.c:170:9:170:9 | s | false | 170 | 172 |
 | test.cpp:18:8:18:10 | call to get | true | 19 | 19 |
 | test.cpp:31:7:31:13 | ... == ... | false | 30 | 30 |
 | test.cpp:31:7:31:13 | ... == ... | false | 34 | 34 |
diff --git a/cpp/ql/test/library-tests/controlflow/guards/GuardsEnsure.expected b/cpp/ql/test/library-tests/controlflow/guards/GuardsEnsure.expected
index f9eaced1276a..45d63f6dd536 100644
--- a/cpp/ql/test/library-tests/controlflow/guards/GuardsEnsure.expected
+++ b/cpp/ql/test/library-tests/controlflow/guards/GuardsEnsure.expected
@@ -234,6 +234,21 @@ unary
 | test.c:109:9:109:23 | ... \|\| ... | test.c:109:9:109:9 | x | != | 0 | 113 | 113 |
 | test.c:109:9:109:23 | ... \|\| ... | test.c:109:19:109:19 | y | >= | 0 | 113 | 113 |
 | test.c:109:19:109:23 | ... < ... | test.c:109:19:109:19 | y | >= | 0 | 113 | 113 |
+| test.c:126:7:126:7 | 1 | test.c:126:7:126:7 | 1 | != | 0 | 126 | 126 |
+| test.c:126:7:126:7 | 1 | test.c:126:7:126:7 | 1 | != | 0 | 126 | 128 |
+| test.c:126:7:126:7 | 1 | test.c:126:7:126:7 | 1 | != | 0 | 131 | 131 |
+| test.c:126:7:126:7 | 1 | test.c:126:7:126:7 | 1 | != | 0 | 131 | 132 |
+| test.c:126:7:126:7 | 1 | test.c:126:7:126:7 | 1 | != | 0 | 134 | 123 |
+| test.c:126:7:126:28 | ... && ... | test.c:126:7:126:7 | 1 | != | 0 | 126 | 128 |
+| test.c:126:7:126:28 | ... && ... | test.c:126:12:126:26 | call to test3_condition | != | 0 | 126 | 128 |
+| test.c:126:12:126:26 | call to test3_condition | test.c:126:12:126:26 | call to test3_condition | != | 0 | 126 | 128 |
+| test.c:131:7:131:7 | b | test.c:131:7:131:7 | b | != | 0 | 131 | 132 |
+| test.c:137:7:137:7 | 0 | test.c:137:7:137:7 | 0 | == | 0 | 142 | 136 |
+| test.c:146:7:146:8 | ! ... | test.c:146:7:146:8 | ! ... | != | 0 | 146 | 147 |
+| test.c:152:8:152:8 | p | test.c:152:8:152:8 | p | != | 0 | 152 | 154 |
+| test.c:158:8:158:9 | ! ... | test.c:158:8:158:9 | ! ... | != | 0 | 158 | 160 |
+| test.c:164:8:164:8 | s | test.c:164:8:164:8 | s | != | 0 | 164 | 166 |
+| test.c:170:8:170:9 | ! ... | test.c:170:8:170:9 | ! ... | != | 0 | 170 | 172 |
 | test.cpp:18:8:18:10 | call to get | test.cpp:18:8:18:10 | call to get | != | 0 | 19 | 19 |
 | test.cpp:31:7:31:13 | ... == ... | test.cpp:31:7:31:7 | x | != | -1 | 30 | 30 |
 | test.cpp:31:7:31:13 | ... == ... | test.cpp:31:7:31:7 | x | != | -1 | 34 | 34 |
diff --git a/cpp/ql/test/library-tests/controlflow/guards/test.c b/cpp/ql/test/library-tests/controlflow/guards/test.c
index 186244d4fca2..207e23baa0e3 100644
--- a/cpp/ql/test/library-tests/controlflow/guards/test.c
+++ b/cpp/ql/test/library-tests/controlflow/guards/test.c
@@ -147,3 +147,27 @@ void test5(int x) {
     test3();
   }
 }
+
+void test6(char* p) {
+    if(p) {
+
+    }
+}
+
+void test7(char* p) {
+    if(!p) {
+        
+    }
+}
+
+void test8(short s) {
+    if(s) {
+
+    }
+}
+
+void test9(short s) {
+    if(!s) {
+        
+    }
+}
\ No newline at end of file