diff --git a/src/debug.h b/src/debug.h
index 8cf5d4c5e2..4f90969f3e 100644
--- a/src/debug.h
+++ b/src/debug.h
@@ -25,6 +25,7 @@
 // Enable various GAP debugging features
 #define COUNT_BAGS
 #define COUNT_OPERS
+#define DEBUG_GMP 1
 #else
 #define GAP_ASSERT(x)
 #endif