diff --git a/string.c b/string.c
index a28d682a84..7c3a790fa3 100644
--- a/string.c
+++ b/string.c
@@ -344,6 +344,10 @@ fstr_update_callback(st_data_t *key, st_data_t *value, st_data_t data, int exist
 
         if (rb_objspace_garbage_object_p(str)) {
             arg->fstr = Qundef;
+            // When RSTRING_FSTR strings are swept, they call `st_delete`.
+            // To avoid a race condition if an equivalent string was inserted
+            // we must remove the flag immediately.
+            FL_UNSET_RAW(str, RSTRING_FSTR);
             return ST_DELETE;
         }
 
diff --git a/version.h b/version.h
index ecddbf549c..cc73220a98 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 7
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 131
+#define RUBY_PATCHLEVEL 132
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"