diff --git a/js/src/old-configure.in b/js/src/old-configure.in
index c2dbcfaffeb8..ab899d30cb08 100644
--- a/js/src/old-configure.in
+++ b/js/src/old-configure.in
@@ -627,6 +627,11 @@ case "$target" in
         fi
         LIBS="$LIBS kernel32.lib user32.lib gdi32.lib winmm.lib wsock32.lib advapi32.lib"
         MOZ_DEBUG_LDFLAGS='-DEBUG'
+        if test "$HOST_OS_ARCH" != "WINNT"; then
+          # %_PDB% is a special signal to emit only the PDB basename. This
+          # avoids problems in Windows tools that don't like forward-slashes.
+          MOZ_DEBUG_LDFLAGS="$MOZ_DEBUG_LDFLAGS -PDBALTPATH:%_PDB%"
+        fi
         MOZ_OPTIMIZE_FLAGS="-O2"
         MOZ_FIX_LINK_PATHS=
         LDFLAGS="$LDFLAGS -LARGEADDRESSAWARE"
diff --git a/old-configure.in b/old-configure.in
index 01e314fcb3bb..26e3d65079d9 100644
--- a/old-configure.in
+++ b/old-configure.in
@@ -736,6 +736,11 @@ case "$target" in
         CXXFLAGS="$CXXFLAGS -D_SILENCE_TR1_NAMESPACE_DEPRECATION_WARNING"
         LIBS="$LIBS user32.lib gdi32.lib winmm.lib wsock32.lib advapi32.lib secur32.lib"
         MOZ_DEBUG_LDFLAGS='-DEBUG'
+        if test "$HOST_OS_ARCH" != "WINNT"; then
+          # %_PDB% is a special signal to emit only the PDB basename. This
+          # avoids problems in Windows tools that don't like forward-slashes.
+          MOZ_DEBUG_LDFLAGS="$MOZ_DEBUG_LDFLAGS -PDBALTPATH:%_PDB%"
+        fi
         # Use a higher optimization level for clang-cl, so we can come closer
         # to MSVC's performance numbers (see bug 1443590).
         if test -n "$CLANG_CL"; then