Index: test/join.test
==================================================================
--- test/join.test
+++ test/join.test
@@ -660,11 +660,20 @@
 jointest join-12.5 65 {1 {at most 64 tables in a join}}
 jointest join-12.6 66 {1 {at most 64 tables in a join}}
 jointest join-12.7 127 {1 {at most 64 tables in a join}}
 jointest join-12.8 128 {1 {at most 64 tables in a join}}
 jointest join-12.9 1000 {1 {at most 64 tables in a join}}
-jointest join-12.10 65534 {1 {at most 64 tables in a join}}
-jointest join-12.11 65535 {1 {too many references to "t14": max 65535}}
-jointest join-12.12 65536 {1 {too many references to "t14": max 65535}}
-jointest join-12.13 65537 {1 {too many references to "t14": max 65535}}
+
+# If SQLite is built with SQLITE_MEMDEBUG, then the huge number of realloc()
+# calls made by the following test cases are too time consuming to run.
+# Without SQLITE_MEMDEBUG, realloc() is fast enough that these are not
+# a problem.
+ifcapable pragma&&compileoption_diags {
+  if {[lsearch [db eval {PRAGMA compile_options}] MEMDEBUG]<0} {
+    jointest join-12.10 65534 {1 {at most 64 tables in a join}}
+    jointest join-12.11 65535 {1 {too many references to "t14": max 65535}}
+    jointest join-12.12 65536 {1 {too many references to "t14": max 65535}}
+    jointest join-12.13 65537 {1 {too many references to "t14": max 65535}}
+  }
+}
 
 finish_test