diff --git a/cmake-3.20.4-glibc_libdl.patch b/cmake-3.20.4-glibc_libdl.patch
new file mode 100644
index 0000000..1c90af4
--- /dev/null
+++ b/cmake-3.20.4-glibc_libdl.patch
@@ -0,0 +1,28 @@
+diff -up cmake-3.20.4/Source/kwsys/testDynamicLoader.cxx.libdl cmake-3.20.4/Source/kwsys/testDynamicLoader.cxx
+--- cmake-3.20.4/Source/kwsys/testDynamicLoader.cxx.libdl	2021-06-14 10:05:49.000000000 -0500
++++ cmake-3.20.4/Source/kwsys/testDynamicLoader.cxx	2021-06-18 14:17:50.990852438 -0500
+@@ -8,6 +8,13 @@
+ #  include <be/kernel/OS.h> /* disable_debugger() API. */
+ #endif
+ 
++#ifdef __linux__
++#include <gnu/lib-names.h>
++#ifndef LIBDL_SO
++#define LIBDL_SO "libdl.so.2"
++#endif
++#endif
++
+ // Work-around CMake dependency scanning limitation.  This must
+ // duplicate the above list of headers.
+ #if 0
+@@ -107,8 +114,8 @@ int testDynamicLoader(int argc, char* ar
+   // This one is actually fun to test, since dlopen is by default
+   // loaded...wonder why :)
+   res += TestDynamicLoader("foobar.lib", "dlopen", 0, 1, 0);
+-  res += TestDynamicLoader("libdl.so", "dlopen", 1, 1, 1);
+-  res += TestDynamicLoader("libdl.so", "TestDynamicLoader", 1, 0, 1);
++  res += TestDynamicLoader(LIBDL_SO, "dlopen", 1, 1, 1);
++  res += TestDynamicLoader(LIBDL_SO, "TestDynamicLoader", 1, 0, 1);
+ #endif
+   // Now try on the generated library
+   std::string libname = GetLibName(KWSYS_NAMESPACE_STRING "TestDynload");
diff --git a/cmake.spec b/cmake.spec
index e19b767..5933149 100644
--- a/cmake.spec
+++ b/cmake.spec
@@ -109,6 +109,10 @@ Patch102:       %{name}-mingw-dl.patch
 # memory-hungry tests when building on koji builders with *lots* of cores
 # so limit it to some reasonable number (4)
 Patch103:       cmake-3.20-CPACK_THREADS.patch
+# (upstreamable)
+# https://bugzilla.redhat.com/show_bug.cgi?id=1972535
+# fix FTBFS
+Patch104:       cmake-3.20.4-glibc_libdl.patch
 
 # Patch for renaming on EPEL
 %if 0%{?name_suffix:1}
@@ -521,6 +525,7 @@ popd
 %changelog
 * Fri Jun 18 2021 Rex Dieter <rdieter@fedoraproject.org> - 3.20.4-1
 - cmake-3.20.4 (#1942118)
+- workaround libdl-related FTBFS (#1972535)
 
 * Sun May 30 2021 Rex Dieter <rdieter@fedoraproject.org> - 3.20.3-1
 - cmake-3.20.3