diff --git a/test/tools/llvm-cov/prevent_false_instantiations.h b/test/tools/llvm-cov/prevent_false_instantiations.h
index 667ebde6d16..a8c72076d16 100644
--- a/test/tools/llvm-cov/prevent_false_instantiations.h
+++ b/test/tools/llvm-cov/prevent_false_instantiations.h
@@ -1,9 +1,11 @@
 // Checks that function instantiations don't go to a wrong file.
 
-// CHECK-NOT: {{_Z5func[1,2]v}}
+// INSTANTIATION-NOT: {{_Z5func[1,2]v}}
+// NAN-NOT: 0{{[ \t]+}}nan%{{[ \t]+}}0{{[ \t]+}}nan%
 
 // RUN: llvm-profdata merge %S/Inputs/prevent_false_instantiations.proftext -o %t.profdata
-// RUN: llvm-cov show %S/Inputs/prevent_false_instantiations.covmapping -instr-profile %t.profdata -filename-equivalence %s | FileCheck %s
+// RUN: llvm-cov show %S/Inputs/prevent_false_instantiations.covmapping -instr-profile %t.profdata -filename-equivalence %s | FileCheck %s -check-prefix=INSTANTIATION
+// RUN: llvm-cov report %S/Inputs/prevent_false_instantiations.covmapping -instr-profile %t.profdata | FileCheck %s -check-prefix=NAN
 
 #define DO_SOMETHING() \
   do {                 \
diff --git a/tools/llvm-cov/CoverageSummaryInfo.h b/tools/llvm-cov/CoverageSummaryInfo.h
index c393b00d32a..a8902042403 100644
--- a/tools/llvm-cov/CoverageSummaryInfo.h
+++ b/tools/llvm-cov/CoverageSummaryInfo.h
@@ -47,6 +47,8 @@ struct RegionCoverageInfo {
   bool isFullyCovered() const { return Covered == NumRegions; }
 
   double getPercentCovered() const {
+    if (NumRegions == 0)
+      return 0.0;
     return double(Covered) / double(NumRegions) * 100.0;
   }
 };
@@ -83,6 +85,8 @@ struct LineCoverageInfo {
   bool isFullyCovered() const { return Covered == (NumLines - NonCodeLines); }
 
   double getPercentCovered() const {
+    if (NumLines - NonCodeLines == 0)
+      return 0.0;
     return double(Covered) / double(NumLines - NonCodeLines) * 100.0;
   }
 };
@@ -109,6 +113,8 @@ struct FunctionCoverageInfo {
   bool isFullyCovered() const { return Executed == NumFunctions; }
 
   double getPercentCovered() const {
+    if (NumFunctions == 0)
+      return 0.0;
     return double(Executed) / double(NumFunctions) * 100.0;
   }
 };