diff --git a/modules/ECMAddAppIcon.cmake b/modules/ECMAddAppIcon.cmake
--- a/modules/ECMAddAppIcon.cmake
+++ b/modules/ECMAddAppIcon.cmake
@@ -17,9 +17,10 @@
 #   <size>-<other_text>.png
 #
 # will be added to the executable target whose sources are specified by
-# ``<sources_var>`` on platforms that support it (Windows and Mac OS X).
-# Other icon files are ignored but on Mac SVG files can be supported and
-# it is thus possible to mix those with png files in a single macro call.
+# ``<sources_var>`` (either a target or a list of source files) on platforms 
+# that support it (Windows and Mac OS X). Other icon files are ignored but on 
+# Mac SVG files can be supported and it is thus possible to mix those with png 
+# files in a single macro call.
 #
 # ``<size>`` is a numeric pixel size (typically 16, 32, 48, 64, 128 or 256).
 # ``<other_text>`` can be any other text. See the platform notes below for any
@@ -113,6 +114,16 @@
         message(FATAL_ERROR "Unexpected arguments to ecm_add_app_icon: ${ARG_UNPARSED_ARGUMENTS}")
     endif()
 
+    # Supports adding sources to both source lists and targets.
+    macro(add_sources sources)
+        if(TARGET ${sources})
+            cmake_minimum_required(VERSION 3.1)
+            target_sources(${sources} PRIVATE ${ARGN})
+        else()
+            set(${sources} ${${sources}} ${ARGN} PARENT_SCOPE)
+        endif()
+    endmacro()
+
     if(APPLE)
         find_program(KSVG2ICNS NAMES ksvg2icns)
         foreach(icon ${ARG_ICONS})
@@ -129,7 +140,7 @@
                     # install the icns file we just created
                     get_filename_component(icon_name ${icon_full} NAME_WE)
                     set(MACOSX_BUNDLE_ICON_FILE ${icon_name}.icns PARENT_SCOPE)
-                    set(${appsources} "${${appsources}};${CMAKE_CURRENT_BINARY_DIR}/${icon_name}.icns" PARENT_SCOPE)
+                    add_sources(${appsources} ${CMAKE_CURRENT_BINARY_DIR}/${icon_name}.icns)
                     set_source_files_properties(${CMAKE_CURRENT_BINARY_DIR}/${icon_name}.icns PROPERTIES MACOSX_PACKAGE_LOCATION Resources)
                     # we're done now
                     return()
@@ -244,7 +255,7 @@
             endforeach()
 
             create_windows_icon_and_rc(IcoTool::IcoTool "${icotool_args}" "${windows_icons_modern}")
-            set(${appsources} "${${appsources}};${_outfilename}.rc" PARENT_SCOPE)
+            add_sources(${appsources} ${_outfilename}.rc)
 
         # standard png2ico has no rcfile argument
         elseif(Png2Ico_FOUND AND NOT Png2Ico_HAS_RCFILE_ARGUMENT AND windows_icons_classic)
@@ -253,7 +264,7 @@
             list(APPEND png2ico_args "${windows_icons_classic}")
 
             create_windows_icon_and_rc(Png2Ico::Png2Ico "${png2ico_args}" "${windows_icons_classic}")
-            set(${appsources} "${${appsources}};${_outfilename}.rc" PARENT_SCOPE)
+            add_sources(${appsources} ${_outfilename}.rc)
 
         # png2ico from kdewin provides rcfile argument
         elseif(Png2Ico_FOUND AND windows_icons_classic)
@@ -268,7 +279,7 @@
                   WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
               )
 
-            set(${appsources} "${${appsources}};${_outfilename}.rc" PARENT_SCOPE)
+            add_sources(${appsources} ${_outfilename}.rc)
         # else none of the supported tools was found
         else()
             message(WARNING "Unable to find the png2ico or icotool utilities or icons in matching sizes - application will not have an application icon!")
@@ -350,7 +361,7 @@
 
             # Append the icns file to the sources list so it will be a dependency to the
             # main target
-            set(${appsources} "${${appsources}};${_outfilename}.icns" PARENT_SCOPE)
+            add_sources(${appsources} ${_outfilename}.icns)
 
             # Install the icon into the Resources dir in the bundle
             set_source_files_properties("${_outfilename}.icns" PROPERTIES MACOSX_PACKAGE_LOCATION Resources)