diff --git a/LayoutTests/ChangeLog b/LayoutTests/ChangeLog
index a8a3ca18f9a8..c86e28df6895 100644
--- a/LayoutTests/ChangeLog
+++ b/LayoutTests/ChangeLog
@@ -1,3 +1,23 @@
+2017-09-27  Fujii Hironori  <Hironori.Fujii@sony.com>
+
+        [REGRESSION] word-spacing property is incorrectly applied
+        https://bugs.webkit.org/show_bug.cgi?id=142086
+        <rdar://problem/19985240>
+
+        Reviewed by Zalan Bujtas.
+
+        * platform/gtk/TestExpectations: Unmark
+        fast/text/word-space-between-inlines.html
+        * platform/mac/TestExpectations: Unmark
+        fast/css/word-spacing-between-blocks.html,
+        fast/css/word-spacing-between-inlines.html,
+        fast/css/word-spacing-characters.html and
+        fast/text/word-space-between-inlines.html.
+        * platform/gtk/fast/css/word-space-extra-expected.txt:
+        Rebaselined.
+        * platform/mac/fast/css/word-space-extra-expected.png: Ditto.
+        * platform/mac/fast/css/word-space-extra-expected.txt: Ditto.
+
 2017-09-27  Zalan Bujtas  <zalan@apple.com>
 
         Deferred image size change makes image-load-on-delay.html flaky.
diff --git a/LayoutTests/platform/mac/TestExpectations b/LayoutTests/platform/mac/TestExpectations
index 41c24d74263d..5f6bff61cff9 100644
--- a/LayoutTests/platform/mac/TestExpectations
+++ b/LayoutTests/platform/mac/TestExpectations
@@ -1052,12 +1052,6 @@ fast/canvas/canvas-fillRect-gradient-shadow.html [ Pass Failure ]
 # SVG gradients are not bit-for-bit equivalent through a scale.
 webkit.org/b/142192 svg/transforms/transformed-text-fill-gradient.html [ ImageOnlyFailure ]
 
-# Word-spacing is incorrectly applied
-webkit.org/b/142086 fast/css/word-spacing-between-blocks.html [ ImageOnlyFailure ]
-webkit.org/b/142086 fast/css/word-spacing-between-inlines.html [ ImageOnlyFailure ]
-webkit.org/b/142086 fast/css/word-spacing-characters.html [ ImageOnlyFailure ]
-webkit.org/b/142086 fast/text/word-space-between-inlines.html [ ImageOnlyFailure ]
-
 # Underlines' starting and ending positions need to be pixel-snapped
 webkit.org/b/142087 fast/css3-text/css3-text-decoration/no-gap-between-two-rounded-textboxes.html [ ImageOnlyFailure ]
 webkit.org/b/142087 fast/css3-text/css3-text-decoration/text-decoration-skip/text-decoration-skip-ink-inherit.html [ ImageOnlyFailure ]
diff --git a/LayoutTests/platform/mac/fast/css/word-space-extra-expected.png b/LayoutTests/platform/mac/fast/css/word-space-extra-expected.png
index eb0dff80f4ae..90e4c18f3214 100644
Binary files a/LayoutTests/platform/mac/fast/css/word-space-extra-expected.png and b/LayoutTests/platform/mac/fast/css/word-space-extra-expected.png differ
diff --git a/LayoutTests/platform/mac/fast/css/word-space-extra-expected.txt b/LayoutTests/platform/mac/fast/css/word-space-extra-expected.txt
index b1a6b15c00be..18cd17b05457 100644
--- a/LayoutTests/platform/mac/fast/css/word-space-extra-expected.txt
+++ b/LayoutTests/platform/mac/fast/css/word-space-extra-expected.txt
@@ -441,7 +441,7 @@ layer at (0,0) size 785x2404
               text run at (371,200) width 142: " elements too"
           RenderText {#text} at (512,198) size 776x36
             text run at (512,198) width 264: ". (with monospace font from"
-            text run at (0,216) width 148: "elements to too) "
+            text run at (0,216) width 168: "elements to too) "
         RenderText {#text} at (0,0) size 0x0
         RenderBR {BR} at (0,0) size 0x0
         RenderBR {BR} at (0,234) size 0x18
diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index f4b24787d2f3..0c0bdf63dfde 100644
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,23 @@
+2017-09-27  Fujii Hironori  <Hironori.Fujii@sony.com>
+
+        [REGRESSION] word-spacing property is incorrectly applied
+        https://bugs.webkit.org/show_bug.cgi?id=142086
+        <rdar://problem/19985240>
+
+        Reviewed by Zalan Bujtas.
+
+        word-spacing property isn't applied to text nodes with starting
+        with '\n' if the kerning enabled. In Bug 165796, only ' ' and '\t'
+        are treated for word-spacing, but '\n'. It should be treated as
+        well.
+
+        Test: fast/text/word-space-between-inlines.html
+
+        * rendering/RenderBlockLineLayout.cpp:
+        (WebCore::setLogicalWidthForTextRun): Use
+        FontCascade::treatAsSpace() instead of checking explicitly by
+        comparing with ' ' and '\t'.
+
 2017-09-27  Zan Dobersek  <zdobersek@igalia.com>
 
         [Cairo] Remove unnecessary cairo.h includes
diff --git a/Source/WebCore/rendering/RenderBlockLineLayout.cpp b/Source/WebCore/rendering/RenderBlockLineLayout.cpp
index ac7cfbe05a34..81cbc248c12c 100644
--- a/Source/WebCore/rendering/RenderBlockLineLayout.cpp
+++ b/Source/WebCore/rendering/RenderBlockLineLayout.cpp
@@ -504,7 +504,7 @@ static inline void setLogicalWidthForTextRun(RootInlineBox* lineBox, BidiRun* ru
                     &wordMeasurement.fallbackFonts, &overflow);
                 UChar c = renderer.characterAt(wordMeasurement.startOffset);
                 // renderer.width() omits word-spacing value for leading whitespace, so let's just add it back here.
-                if (!atFirstWordMeasurement && (c == ' ' || c == '\t'))
+                if (!atFirstWordMeasurement && FontCascade::treatAsSpace(c))
                     measuredWidth += renderer.style().fontCascade().wordSpacing();
             } else
                 measuredWidth += wordMeasurement.width;