diff --git a/esac-syntax-fix.diff b/esac-syntax-fix.diff
new file mode 100644
index 0000000..e863798
--- /dev/null
+++ b/esac-syntax-fix.diff
@@ -0,0 +1,103 @@
+--- mpich-3.4.1/src/mpl/configure.ac~	2021-01-20 19:04:56.000000000 +0100
++++ mpich-3.4.1/src/mpl/configure.ac	2021-05-17 09:45:20.178904241 +0200
+@@ -426,99 +426,7 @@
+ 
+     linux86_cycle|linux86_cycle_2)
+     
+-# The following AC_TRY_RUN statements are needed because x86_64 compilers
+-# usually know about rdtscp but the cpu may or may not actually implement the
+-# feature.  This is not cross-compile safe, unfortunately.  In the long run we
+-# should allow the user to override this with a configure flag.
+-    AC_CACHE_CHECK([that linux86 cycle counter is available],
+-        pac_cv_linux86_cycle,
+-            AC_TRY_RUN([
+-int main()
+-{
+-    /* rdtscp */
+-    long long var, *var_ptr=&var;
+-    __asm__ __volatile__("rdtscp; shl \$32, %%rdx; or %%rdx, %%rax" : "=a" (*var_ptr) : : "ecx", "rdx");
+-    return 0;
+-}
+-            ],pac_cv_linux86_cycle=rdtscp,
+-                AC_TRY_RUN([[
+-int main()
+-{
+-    /* cpuid 64 */
+-    long long var, *var_ptr=&var;
+-    __asm__ __volatile__("push %%rbx ; cpuid ; rdtsc ; pop %%rbx ; shl $32, %%rdx; or %%rdx, %%rax" : "=a" (*var_ptr) : : "ecx", "rdx");
+-    return 0;
+-}
+-                ]],pac_cv_linux86_cycle=cpuid_rdtsc64,
+-                    AC_TRY_RUN([[[
+-int main()
+-{
+-    /* cpuid 32 */
+-    long long var, *var_ptr=&var;
+-    __asm__ __volatile__("push %%ebx ; cpuid ; rdtsc ; pop %%ebx" : "=A" (*var_ptr) : : "ecx");
+-    return 0;
+-}
+-                    ]]],pac_cv_linux86_cycle=cpuid_rdtsc32,
+-                        AC_TRY_RUN([[[[
+-int main()
+-{
+-    /* simple */
+-    long long var, *var_ptr=&var;
+-    __asm__ __volatile__("rdtsc" : "=A" (*var_ptr));
+-    return 0;
+-}
+-                        ]]]],pac_cv_linux86_cycle=rdtsc,
+-                        pac_cv_linux86_cycle=no)
+-                    )
+-                ),
+-dnl The if-cross-compiling clause from the first AC_TRY_RUN.  Hope that if the
+-dnl compiler knows about the instruction then it's supported by the target
+-dnl platform.
+-                AC_TRY_COMPILE(,[[
+-                    long long var, *var_ptr=&var;
+-                    __asm__ __volatile__("rdtscp; shl \$32, %%rdx; or %%rdx, %%rax" : "=a" (*var_ptr) : : "ecx", "rdx");
+-                ]],pac_cv_linux86_cycle=rdtscp,
+-                    AC_TRY_COMPILE(,[[[
+-                        long long var, *var_ptr=&var;
+-                        __asm__ __volatile__("push %%rbx ; cpuid ; rdtsc ; pop %%rbx ; shl $32, %%rdx; or %%rdx, %%rax" : "=a" (*var_ptr) : : "ecx", "rdx");
+-                    ]]],pac_cv_linux86_cycle=cpuid_rdtsc64,
+-                        AC_TRY_COMPILE(,[[[[
+-                            long long var, *var_ptr=&var;
+-                            __asm__ __volatile__("push %%ebx ; cpuid ; rdtsc ; pop %%ebx" : "=A" (*var_ptr) : : "ecx");
+-                        ]]]],pac_cv_linux86_cycle=cpuid_rdtsc32,
+-                            AC_TRY_COMPILE(,[[[[[
+-                                long long var, *var_ptr=&var;
+-                                __asm__ __volatile__("rdtsc" : "=A" (*var_ptr));
+-                            ]]]]],pac_cv_linux86_cycle=rdtsc,
+-                            pac_cv_linux86_cycle=no)
+-                        )
+-                    )
+-                )
+-            )
+-    )
+-
+-    case "$pac_cv_linux86_cycle" in
+-        "rdtscp")
+-            AC_DEFINE(LINUX86_CYCLE_RDTSCP,1,[Define which x86 cycle counter to use])
+-	    ;;
+-        "cpuid_rdtsc64")
+-            AC_DEFINE(LINUX86_CYCLE_CPUID_RDTSC64,1,[Define which x86 cycle counter to use])
+-            ;;
+-        "cpuid_rdtsc32")
+-            AC_DEFINE(LINUX86_CYCLE_CPUID_RDTSC32,1,[Define which x86 cycle counter to use])
+-	    ;;
+-        "rdtsc")
+-            AC_DEFINE(LINUX86_CYCLE_RDTSC,1,[Define which x86 cycle counter to use])
+-	    ;;
+-        *)
+-            cpu_gcc_x86_cycle=no
+-	    ;;
+-    esac
+-
+-    if test "$cpu_gcc_x86_cycle" = "no" ; then
+-        AC_MSG_ERROR([Linux86 cycle counter is not available on this system and or with the $CC compiler])
+-    fi
+-    MPL_TIMER_TYPE="long long"
++    AC_MSG_ERROR([Linux86 cycle counter is not available])
+     ;;
+ 
+     gcc_ia64_cycle)
diff --git a/mpich.spec b/mpich.spec
index 519b8a3..959f3de 100644
--- a/mpich.spec
+++ b/mpich.spec
@@ -17,8 +17,9 @@ Patch1:         0001-Drop-real128.patch
 Patch3:         fix_wrapper_flags.patch
 # https://github.com/pmodels/mpich/issues/4534
 Patch4:         0001-Revert-Remove-use-of-vasprintf.patch
+Patch5:         esac-syntax-fix.diff
 
-BuildRequires: make
+BuildRequires:  make
 BuildRequires:  gcc
 BuildRequires:  gcc-c++
 BuildRequires:  gcc-gfortran
@@ -119,6 +120,11 @@ mpich support for Python 3.
 
 %patch4 -p1
 
+# There seems to be some syntax error, but I cannot figure out what it
+# is (";;" is missing, but adding it doesn't fix things). Since we use
+# clock_gettime anyway, just rip out the whole block.
+%patch5 -p1
+
 %build
 ./autogen.sh
 
@@ -251,6 +257,9 @@ make check VERBOSE=1 \
 %{python3_sitearch}/%{name}.pth
 
 %changelog
+* Mon May 17 2021 Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> - 3.4.1-1
+- Rip out part of configure.ac to fix build under autoconf-2.71 (#1943036)
+
 * Wed Jan 27 2021 Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> - 3.4.1-1
 - Update to latest version (#1912981)