diff --git a/clang/lib/Format/Format.cpp b/clang/lib/Format/Format.cpp
--- a/clang/lib/Format/Format.cpp
+++ b/clang/lib/Format/Format.cpp
@@ -3447,11 +3447,11 @@
     tooling::Replacements Replaces =
         Formatter(*Env, Style, Status).process().first;
     // add a replacement to remove the "x = " from the result.
-    if (!Replaces.add(tooling::Replacement(FileName, 0, 4, ""))) {
-      // apply the reformatting changes and the removal of "x = ".
-      if (applyAllReplacements(Code, Replaces))
-        return {Replaces, 0};
-    }
+    Replaces = Replaces.merge(
+        tooling::Replacements(tooling::Replacement(FileName, 0, 4, "")));
+    // apply the reformatting changes and the removal of "x = ".
+    if (applyAllReplacements(Code, Replaces))
+      return {Replaces, 0};
     return {tooling::Replacements(), 0};
   }
 
diff --git a/clang/unittests/Format/FormatTestJson.cpp b/clang/unittests/Format/FormatTestJson.cpp
--- a/clang/unittests/Format/FormatTestJson.cpp
+++ b/clang/unittests/Format/FormatTestJson.cpp
@@ -251,5 +251,25 @@
                      Style);
 }
 
+TEST_F(FormatTestJson, StartsWithWhitespaces) {
+  FormatStyle Style = getLLVMStyle(FormatStyle::LK_Json);
+  EXPECT_EQ("{\n"
+            "  \"name\": 1\n"
+            "}",
+            format(" {\n"
+                   "  \"name\": 1\n"
+                   "}",
+                   Style));
+
+  // FIXME: The block below is over-indented.
+  EXPECT_EQ("    {\n"
+            "      \"name\": 1\n"
+            "    }",
+            format("\n{\n"
+                   "  \"name\": 1\n"
+                   "}",
+                   Style));
+}
+
 } // namespace format
 } // end namespace clang