diff --git a/layout/generic/nsTextFrame.h b/layout/generic/nsTextFrame.h
index df6030c998af..0cf3da50ed5d 100644
--- a/layout/generic/nsTextFrame.h
+++ b/layout/generic/nsTextFrame.h
@@ -182,6 +182,7 @@ public:
 #endif
 
   float GetFontSizeInflation() const;
+  bool IsCurrentFontInflation(float aInflation) const;
   bool HasFontSizeInflation() const {
     return (GetStateBits() & TEXT_HAS_FONT_INFLATION) != 0;
   }
diff --git a/layout/generic/nsTextFrameThebes.cpp b/layout/generic/nsTextFrameThebes.cpp
index e524fcd08257..67704bd85f0c 100644
--- a/layout/generic/nsTextFrameThebes.cpp
+++ b/layout/generic/nsTextFrameThebes.cpp
@@ -6710,6 +6710,10 @@ nsTextFrame::AddInlineMinWidthForFlow(nsRenderingContext *aRenderingContext,
   }
 }
 
+bool nsTextFrame::IsCurrentFontInflation(float aInflation) const {
+  return fabsf(aInflation - GetFontSizeInflation()) < 1e-6;
+}
+
 // XXX Need to do something here to avoid incremental reflow bugs due to
 // first-line and first-letter changing min-width
 /* virtual */ void
@@ -6719,7 +6723,7 @@ nsTextFrame::AddInlineMinWidth(nsRenderingContext *aRenderingContext,
   float inflation = nsLayoutUtils::FontSizeInflationFor(this);
   TextRunType trtype = (inflation == 1.0f) ? eNotInflated : eInflated;
 
-  if (trtype == eInflated && inflation != GetFontSizeInflation()) {
+  if (trtype == eInflated && !IsCurrentFontInflation(inflation)) {
     // FIXME: Ideally, if we already have a text run, we'd move it to be
     // the uninflated text run.
     ClearTextRun(nsnull, nsTextFrame::eInflated);
@@ -6855,7 +6859,7 @@ nsTextFrame::AddInlinePrefWidth(nsRenderingContext *aRenderingContext,
   float inflation = nsLayoutUtils::FontSizeInflationFor(this);
   TextRunType trtype = (inflation == 1.0f) ? eNotInflated : eInflated;
 
-  if (trtype == eInflated && inflation != GetFontSizeInflation()) {
+  if (trtype == eInflated && !IsCurrentFontInflation(inflation)) {
     // FIXME: Ideally, if we already have a text run, we'd move it to be
     // the uninflated text run.
     ClearTextRun(nsnull, nsTextFrame::eInflated);
@@ -7395,7 +7399,7 @@ nsTextFrame::ReflowText(nsLineLayout& aLineLayout, nscoord aAvailableWidth,
 
   float fontSizeInflation = nsLayoutUtils::FontSizeInflationFor(this);
 
-  if (fontSizeInflation != GetFontSizeInflation()) {
+  if (!IsCurrentFontInflation(fontSizeInflation)) {
     // FIXME: Ideally, if we already have a text run, we'd move it to be
     // the uninflated text run.
     ClearTextRun(nsnull, nsTextFrame::eInflated);
@@ -7405,7 +7409,7 @@ nsTextFrame::ReflowText(nsLineLayout& aLineLayout, nscoord aAvailableWidth,
     EnsureTextRun(nsTextFrame::eInflated, ctx,
                   lineContainer, aLineLayout.GetLine(), &flowEndInTextRun);
 
-  NS_ABORT_IF_FALSE(GetFontSizeInflation() == fontSizeInflation,
+  NS_ABORT_IF_FALSE(IsCurrentFontInflation(fontSizeInflation),
                     "EnsureTextRun should have set font size inflation");
 
   if (mTextRun && iter.GetOriginalEnd() < offset + length) {