diff --git a/NEWS b/NEWS
index a08c2d77a9c..8dbff5e134f 100644
--- a/NEWS
+++ b/NEWS
@@ -6,6 +6,8 @@ PHP                                                                        NEWS
 - COM:
   . Fixed bug #66322 (COMPersistHelper::SaveToFile can save to wrong location).
     (cmb)
+  . Fixed bug #79242 (COM error constants don't match com_exception codes on
+    x86). (cmb)
 
 - CURL:
   . Fixed bug #79019 (Copied cURL handles upload empty file). (cmb)
diff --git a/ext/com_dotnet/com_extension.c b/ext/com_dotnet/com_extension.c
index 7ff0fd0ebd5..c77d0891883 100644
--- a/ext/com_dotnet/com_extension.c
+++ b/ext/com_dotnet/com_extension.c
@@ -341,11 +341,15 @@ PHP_MINIT_FUNCTION(com_dotnet)
 
 #define COM_CONST(x) REGISTER_LONG_CONSTANT(#x, x, CONST_CS|CONST_PERSISTENT)
 
-#define COM_ERR_CONST(x) { \
+#if SIZEOF_ZEND_LONG == 8
+# define COM_ERR_CONST(x) { \
 	zend_long __tmp; \
 	ULongToIntPtr(x, &__tmp); \
 	REGISTER_LONG_CONSTANT(#x, __tmp, CONST_CS|CONST_PERSISTENT); \
 }
+#else
+# define COM_ERR_CONST COM_CONST
+#endif
 
 	COM_CONST(CLSCTX_INPROC_SERVER);
 	COM_CONST(CLSCTX_INPROC_HANDLER);
diff --git a/ext/com_dotnet/tests/bug79242.phpt b/ext/com_dotnet/tests/bug79242.phpt
new file mode 100644
index 00000000000..46c5d8af3b7
--- /dev/null
+++ b/ext/com_dotnet/tests/bug79242.phpt
@@ -0,0 +1,22 @@
+--TEST--
+Bug #79242 (COM error constants don't match com_exception codes)
+--SKIPIF--
+<?php
+if (!extension_loaded('com_dotnet')) die('skip com_dotnet extension not available');
+if (PHP_INT_SIZE != 4) die("skip this test is for 32bit platforms only");
+?>
+--FILE--
+<?php
+var_dump(
+    DISP_E_DIVBYZERO,
+    DISP_E_OVERFLOW,
+    DISP_E_BADINDEX,
+    MK_E_UNAVAILABLE
+);
+?>
+--EXPECT--
+int(-2147352558)
+int(-2147352566)
+int(-2147352565)
+int(-2147221021)
+