diff --git a/src/library/tcltk/R/unix/zzz.R b/src/library/tcltk/R/unix/zzz.R
index 9715367..2ba8d1c 100644
--- a/src/library/tcltk/R/unix/zzz.R
+++ b/src/library/tcltk/R/unix/zzz.R
@@ -41,7 +41,7 @@
         ## installed, and check libX11 is present since this is a
         ## common cause of problems with CRAN binary installs reported
         ## for Rcmdr.
-        DSO <- file.path(libname, pkgname, "libs", .Platform$r_arch, "tcltk.so")
+        DSO <- file.path(libname, pkgname, "libs", .Platform$r_arch, "tcltk.dylib")
         loads <- utils:::macDynLoads(DSO)
         ind <- grep("^/.*libtk[.0-9]+[.]dylib", loads)
         if (length(ind)) {