diff --git a/lib/Epub/Epub/ParsedText.cpp b/lib/Epub/Epub/ParsedText.cpp
index e57d1743..ebe758db 100644
--- a/lib/Epub/Epub/ParsedText.cpp
+++ b/lib/Epub/Epub/ParsedText.cpp
@@ -1006,7 +1006,10 @@ void ParsedText::extractLine(const size_t breakIndex, const int pageWidth, const
         int advance =
             renderer.getKerning(fontId, lastCodepoint(reorderedWordsScratch[wordIdx]),
                                 firstCodepoint(reorderedWordsScratch[wordIdx + 1]), reorderedStylesScratch[wordIdx]);
-        if (reorderedWordsScratch[wordIdx] == " " && reorderedContinuesScratch[wordIdx] &&
+        // wordIdx > 0 mirrors the gap accounting above (which skips index 0): a leading
+        // no-break space must not receive justifyExtra, or the line over-stretches by one
+        // gap and the last word is pushed past the right margin (issue #2185).
+        if (wordIdx > 0 && reorderedWordsScratch[wordIdx] == " " && reorderedContinuesScratch[wordIdx] &&
             effectiveAlignment == CssTextAlign::Justify && !isLastLine) {
           advance += reorderedJustifyExtra;
         }
@@ -1048,7 +1051,8 @@ void ParsedText::extractLine(const size_t breakIndex, const int pageWidth, const
           // Cross-boundary kerning for continuation words
           int advance = renderer.getKerning(fontId, lastCodepoint(lineWords[wordIdx]),
                                             firstCodepoint(lineWords[wordIdx + 1]), lineWordStyles[wordIdx]);
-          if (lineWords[wordIdx] == " " && continuesVec[lastBreakAt + wordIdx] &&
+          // wordIdx > 0: see the LTR branch — a leading no-break space is not a justifiable gap.
+          if (wordIdx > 0 && lineWords[wordIdx] == " " && continuesVec[lastBreakAt + wordIdx] &&
               effectiveAlignment == CssTextAlign::Justify && !isLastLine) {
             advance += justifyExtra;
           }
@@ -1086,7 +1090,10 @@ void ParsedText::extractLine(const size_t breakIndex, const int pageWidth, const
           int advance = wordWidths[lastBreakAt + wordIdx];
           advance += renderer.getKerning(fontId, lastCodepoint(lineWords[wordIdx]),
                                          firstCodepoint(lineWords[wordIdx + 1]), lineWordStyles[wordIdx]);
-          if (lineWords[wordIdx] == " " && continuesVec[lastBreakAt + wordIdx] &&
+          // wordIdx > 0 mirrors the gap accounting above (which skips index 0): a leading
+          // no-break space must not receive justifyExtra, or the line over-stretches by one
+          // gap and the last word is pushed past the right margin (issue #2185).
+          if (wordIdx > 0 && lineWords[wordIdx] == " " && continuesVec[lastBreakAt + wordIdx] &&
               effectiveAlignment == CssTextAlign::Justify && !isLastLine) {
             advance += justifyExtra;
           }