diff --git a/CuTest.c b/CuTest.c
index 8f61199..2ae8cc2 100644
--- a/CuTest.c
+++ b/CuTest.c
@@ -222,7 +222,7 @@ void CuAssertDblEquals_LineMsg(CuTest* tc, const char* file, int line, const cha
 }
 
 void CuAssertPtrEquals_LineMsg(CuTest* tc, const char* file, int line, const char* message, 
-	void* expected, void* actual)
+	const void* expected, const void* actual)
 {
 	char buf[STRING_MAX];
 	if (expected == actual) return;
diff --git a/CuTest.h b/CuTest.h
index 3866107..c7fad9e 100644
--- a/CuTest.h
+++ b/CuTest.h
@@ -69,7 +69,7 @@ void CuAssertDblEquals_LineMsg(CuTest* tc,
 	double expected, double actual, double delta);
 void CuAssertPtrEquals_LineMsg(CuTest* tc, 
 	const char* file, int line, const char* message, 
-	void* expected, void* actual);
+	const void* expected, const void* actual);
 
 /* public assert functions */