diff --git a/CMakeModules/PerformFeatureChecks.cmake b/CMakeModules/PerformFeatureChecks.cmake
index 16c989983d..63395dc356 100644
--- a/CMakeModules/PerformFeatureChecks.cmake
+++ b/CMakeModules/PerformFeatureChecks.cmake
@@ -78,6 +78,10 @@ macro(perform_feature_checks)
     # HAVE_GETTIMEOFDAY is already in use within 2.9 wxWidgets, so use HAVE_GETTIMEOFDAY_FUNC
     check_symbol_exists(gettimeofday "sys/time.h" HAVE_GETTIMEOFDAY_FUNC)
 
+    # Check for Posix getc_unlocked() for improved performance over getc().  Fall back to
+    # getc() on platforms where getc_unlocked() doesn't exist.
+    check_symbol_exists(getc_unlocked "stdio.h" HAVE_GETC_UNLOCKED)
+
     # Generate config.h.
     configure_file(${PROJECT_SOURCE_DIR}/CMakeModules/config.h.cmake
                    ${CMAKE_BINARY_DIR}/config.h)
diff --git a/CMakeModules/config.h.cmake b/CMakeModules/config.h.cmake
index f9cad7c542..35e6e097de 100644
--- a/CMakeModules/config.h.cmake
+++ b/CMakeModules/config.h.cmake
@@ -50,6 +50,9 @@
 #define strnicmp _strnicmp
 #endif
 
+/* Use Posix getc_unlocked() instead of getc() when it's available. */
+#cmakedefine HAVE_GETC_UNLOCKED
+
 /* Warning!!!  Using wxGraphicContext for rendering is experimental. */
 #cmakedefine USE_WX_GRAPHICS_CONTEXT 1
 
diff --git a/common/richio.cpp b/common/richio.cpp
index 4ab811d96c..e264f6ba3d 100644
--- a/common/richio.cpp
+++ b/common/richio.cpp
@@ -28,6 +28,13 @@
 
 #include <richio.h>
 
+
+// Fall back to getc() when getc_unlocked() is not available on the target platform.
+#if !defined( HAVE_GETC_UNLOCKED )
+#define getc_unlocked getc
+#endif
+
+
 // This file defines 3 classes useful for working with DSN text files and is named
 // "richio" after its author, Richard Hollenbeck, aka Dick Hollenbeck.