diff --git a/src/config.c b/src/config.c
index 4e2c74e5d..83651877c 100644
--- a/src/config.c
+++ b/src/config.c
@@ -1007,6 +1007,16 @@ void configSetCommand(client *c) {
       "activerehashing",server.activerehashing) {
     } config_set_bool_field(
       "activedefrag",server.active_defrag_enabled) {
+#ifndef HAVE_DEFRAG
+        if (server.active_defrag_enabled) {
+            server.active_defrag_enabled = 0;
+            addReplyError(c,
+                "Active defragmentation cannot be enabled: it requires a "
+                "Redis server compiled with a modified Jemalloc like the "
+                "one shipped by default with the Redis source distribution");
+            return;
+        }
+#endif
     } config_set_bool_field(
       "protected-mode",server.protected_mode) {
     } config_set_bool_field(
diff --git a/src/server.h b/src/server.h
index 17e12d9d6..bbc121b72 100644
--- a/src/server.h
+++ b/src/server.h
@@ -152,7 +152,7 @@ typedef long long mstime_t; /* millisecond time type. */
 #define CONFIG_DEFAULT_LAZYFREE_LAZY_EXPIRE 0
 #define CONFIG_DEFAULT_LAZYFREE_LAZY_SERVER_DEL 0
 #define CONFIG_DEFAULT_ALWAYS_SHOW_LOGO 0
-#define CONFIG_DEFAULT_ACTIVE_DEFRAG 1
+#define CONFIG_DEFAULT_ACTIVE_DEFRAG 0
 #define CONFIG_DEFAULT_DEFRAG_THRESHOLD_LOWER 10 /* don't defrag when fragmentation is below 10% */
 #define CONFIG_DEFAULT_DEFRAG_THRESHOLD_UPPER 100 /* maximum defrag force at 100% fragmentation */
 #define CONFIG_DEFAULT_DEFRAG_IGNORE_BYTES (100<<20) /* don't defrag if frag overhead is below 100mb */