diff --git a/src/runtime.c b/src/runtime.c
index d91b5672..ad16bf57 100644
--- a/src/runtime.c
+++ b/src/runtime.c
@@ -1089,6 +1089,7 @@ hs_error_t HS_CDECL hs_stream_size(const hs_database_t *db,
 // perusal.
 static UNUSED
 void dumpData(const char *data, size_t len) {
+    if (!data) return;
     DEBUG_PRINTF("BUFFER:");
     for (size_t i = 0; i < len; i++) {
         u8 c = data[i];