diff --git a/clang/lib/Format/WhitespaceManager.cpp b/clang/lib/Format/WhitespaceManager.cpp
--- a/clang/lib/Format/WhitespaceManager.cpp
+++ b/clang/lib/Format/WhitespaceManager.cpp
@@ -445,8 +445,16 @@
 
     unsigned ChangeMinColumn = Changes[i].StartOfTokenColumn;
     int LineLengthAfter = Changes[i].TokenLength;
-    for (unsigned j = i + 1; j != e && Changes[j].NewlinesBefore == 0; ++j)
-      LineLengthAfter += Changes[j].Spaces + Changes[j].TokenLength;
+    for (unsigned j = i + 1; j != e && Changes[j].NewlinesBefore == 0; ++j) {
+      LineLengthAfter += Changes[j].Spaces;
+      // Changes are generally 1:1 with the tokens, but a change could also be
+      // inside of a token, in which case it's counted more than once: once for
+      // the whitespace surrounding the token (!IsInsideToken) and once for
+      // each whitespace change within it (IsInsideToken).
+      // Therefore, changes inside of a token should only count the space.
+      if (!Changes[j].IsInsideToken)
+        LineLengthAfter += Changes[j].TokenLength;
+    }
     unsigned ChangeMaxColumn = Style.ColumnLimit - LineLengthAfter;
 
     // If we are restricted by the maximum column width, end the sequence.
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -12010,6 +12010,16 @@
                "  x = 1;\n"
                "y = 1;\n",
                Alignment);
+
+  Alignment.ReflowComments = true;
+  Alignment.ColumnLimit = 50;
+  EXPECT_EQ("int x   = 0;\n"
+            "int yy  = 1; /// specificlennospace\n"
+            "int zzz = 2;\n",
+            format("int x   = 0;\n"
+                   "int yy  = 1; ///specificlennospace\n"
+                   "int zzz = 2;\n",
+                   Alignment));
 }
 
 TEST_F(FormatTest, AlignConsecutiveDeclarations) {