diff --git a/lib/isc/include/isc/mem.h b/lib/isc/include/isc/mem.h
index b7143bdbdd..2ee8c9e200 100644
--- a/lib/isc/include/isc/mem.h
+++ b/lib/isc/include/isc/mem.h
@@ -190,14 +190,20 @@ extern unsigned int isc_mem_defaultflags;
  * for more information.
  */
 #if HAVE_JEMALLOC
-#include <jemalloc/jemalloc.h>
+
+/*
+ * cmocka.h has confliction definitions with the jemalloc header but we only
+ * need the mallocx symbol from jemalloc.
+ */
+void *
+mallocx(size_t size, int flags);
 
 extern volatile void *isc__mem_malloc;
 
-#define isc_mem_create(cp)                                        \
-	{                                                         \
-		isc__mem_create((cp)_ISC_MEM_FILELINE);           \
-		isc__mem_malloc = mallocx;                        \
+#define isc_mem_create(cp)                                            \
+	{                                                             \
+		isc__mem_create((cp)_ISC_MEM_FILELINE);               \
+		isc__mem_malloc = mallocx;                            \
 		ISC_INSIST(CMM_ACCESS_ONCE(isc__mem_malloc) != NULL); \
 	}
 #else