diff --git a/sharedlib/CMakeLists.txt b/sharedlib/CMakeLists.txt
index e4bf35d0b..2be5ab33d 100644
--- a/sharedlib/CMakeLists.txt
+++ b/sharedlib/CMakeLists.txt
@@ -89,17 +89,24 @@ endif()
 set(CDJPEG_COMPILE_FLAGS
   "-DBMP_SUPPORTED -DGIF_SUPPORTED -DPPM_SUPPORTED -DTARGA_SUPPORTED ${USE_SETMODE}")
 
+set(CJPEG_PNG_SOURCES "")
+if(PNG_SUPPORTED)
+  set(CDJPEG_COMPILE_FLAGS "${CDJPEG_COMPILE_FLAGS} -DPNG_SUPPORTED")
+  set(CJPEG_PNG_SOURCES ../rdpng.c)
+endif()
+
 # Compile a separate version of these source files with 12-bit and 16-bit data
 # precision.
-add_library(cjpeg12 OBJECT ../rdgif.c ../rdppm.c)
+add_library(cjpeg12 OBJECT ../rdgif.c ../rdppm.c ${CJPEG_PNG_SOURCES})
 set_property(TARGET cjpeg12 PROPERTY COMPILE_FLAGS
   "-DBITS_IN_JSAMPLE=12 -DGIF_SUPPORTED -DPPM_SUPPORTED")
-add_library(cjpeg16 OBJECT ../rdgif.c ../rdppm.c)
+add_library(cjpeg16 OBJECT ../rdgif.c ../rdppm.c ${CJPEG_PNG_SOURCES})
 set_property(TARGET cjpeg16 PROPERTY COMPILE_FLAGS
   "-DBITS_IN_JSAMPLE=16 -DGIF_SUPPORTED -DPPM_SUPPORTED")
 add_executable(cjpeg ../cjpeg.c ../cdjpeg.c ../rdbmp.c ../rdgif.c ../rdppm.c
   ../rdjpeg.c
-  ../rdswitch.c ../rdtarga.c $<TARGET_OBJECTS:cjpeg12>
+  ../rdswitch.c ../rdtarga.c ${CJPEG_PNG_SOURCES}
+  $<TARGET_OBJECTS:cjpeg12>
   $<TARGET_OBJECTS:cjpeg16>)
 set_property(TARGET cjpeg PROPERTY COMPILE_FLAGS ${CDJPEG_COMPILE_FLAGS})
 target_link_libraries(cjpeg jpeg)
@@ -114,20 +121,6 @@ set_property(TARGET djpeg16 PROPERTY COMPILE_FLAGS
   "-DBITS_IN_JSAMPLE=16 -DPPM_SUPPORTED")
 
 if(PNG_SUPPORTED)
-  report_option(PNG_SUPPORTED "PNG reading support")
-  set(COMPILE_FLAGS "${COMPILE_FLAGS} -DPNG_SUPPORTED")
-  set(CJPEG_BMP_SOURCES ${CJPEG_BMP_SOURCES} ../rdpng.c)
-endif()
-
-if(PNG_SUPPORTED)
-  # to avoid finding static library from CMake cache
-  unset(PNG_LIBRARY CACHE)
-  unset(PNG_LIBRARY_RELEASE CACHE)
-  unset(PNG_LIBRARY_DEBUG CACHE)
-  unset(ZLIB_LIBRARY CACHE)
-  unset(ZLIB_LIBRARY_RELEASE CACHE)
-  unset(ZLIB_LIBRARY_DEBUG CACHE)
-
   find_package(PNG 1.6 REQUIRED)
   find_package(ZLIB REQUIRED)
   target_include_directories(cjpeg PUBLIC ${PNG_INCLUDE_DIR} ${ZLIB_INCLUDE_DIR})