diff --git a/sys/pc98/i386/machdep.c b/sys/pc98/i386/machdep.c
index 96576ee70863..b4aae08ee3b7 100644
--- a/sys/pc98/i386/machdep.c
+++ b/sys/pc98/i386/machdep.c
@@ -92,6 +92,9 @@
 #include <sys/cons.h>
 
 #ifdef DDB
+#ifndef KDB
+#error KDB must be enabled in order for DDB to work!
+#endif
 #include <ddb/ddb.h>
 #include <ddb/db_sym.h>
 #endif
diff --git a/sys/pc98/pc98/machdep.c b/sys/pc98/pc98/machdep.c
index 96576ee70863..b4aae08ee3b7 100644
--- a/sys/pc98/pc98/machdep.c
+++ b/sys/pc98/pc98/machdep.c
@@ -92,6 +92,9 @@
 #include <sys/cons.h>
 
 #ifdef DDB
+#ifndef KDB
+#error KDB must be enabled in order for DDB to work!
+#endif
 #include <ddb/ddb.h>
 #include <ddb/db_sym.h>
 #endif