diff --git a/mozilla/js/src/jsdhash.c b/mozilla/js/src/jsdhash.c
index 9e8ee097cb0..64f9f3a4a47 100644
--- a/mozilla/js/src/jsdhash.c
+++ b/mozilla/js/src/jsdhash.c
@@ -175,6 +175,7 @@ JS_DHashTableInit(JSDHashTable *table, JSDHashTableOps *ops, void *data,
     if (capacity < JS_DHASH_MIN_SIZE)
         capacity = JS_DHASH_MIN_SIZE;
     log2 = JS_CeilingLog2(capacity);
+    capacity = JS_BIT(log2);
     table->hashShift = JS_DHASH_BITS - log2;
     table->sizeLog2 = log2;
     table->sizeMask = JS_BITMASK(table->sizeLog2);
diff --git a/mozilla/xpcom/ds/pldhash.c b/mozilla/xpcom/ds/pldhash.c
index d5fa2519e8d..3cacb067d04 100644
--- a/mozilla/xpcom/ds/pldhash.c
+++ b/mozilla/xpcom/ds/pldhash.c
@@ -176,6 +176,7 @@ PL_DHashTableInit(PLDHashTable *table, PLDHashTableOps *ops, void *data,
     if (capacity < PL_DHASH_MIN_SIZE)
         capacity = PL_DHASH_MIN_SIZE;
     log2 = PR_CeilingLog2(capacity);
+    capacity = PR_BIT(log2);
     table->hashShift = PL_DHASH_BITS - log2;
     table->sizeLog2 = log2;
     table->sizeMask = PR_BITMASK(table->sizeLog2);