diff --git a/_constraints b/_constraints
index baa391d..2da2be5 100644
--- a/_constraints
+++ b/_constraints
@@ -7,8 +7,8 @@
 		</memoryperjob>
 -->
 		<physicalmemory>
-			<!-- 3400x4 -->
-			<size unit="M">13600</size>
+			<!-- using %%limit_build, plus 200 for kernel -->
+			<size unit="M">3600</size>
 		</physicalmemory>
 	</hardware>
 </constraints>
diff --git a/polymake.changes b/polymake.changes
index 95afd36..9ec5dea 100644
--- a/polymake.changes
+++ b/polymake.changes
@@ -1,3 +1,8 @@
+-------------------------------------------------------------------
+Sat Sep 26 21:03:32 UTC 2020 - Jan Engelhardt <jengelh@inai.de>
+
+- Go back from _constraints file to %limit_build
+
 -------------------------------------------------------------------
 Tue Sep  8 11:27:01 UTC 2020 - Jan Engelhardt <jengelh@inai.de>
 
diff --git a/polymake.spec b/polymake.spec
index eb94faa..88f2439 100644
--- a/polymake.spec
+++ b/polymake.spec
@@ -80,12 +80,15 @@ objects, and other objects.
 %autosetup -p1
 
 %build
-cat /proc/meminfo
 # Not AC.
 ./configure --prefix="%_prefix" --libdir="%_libdir" \
 	--libexecdir="%_libdir/%name-%version" --without-native \
 	CFLAGS="%optflags" CXXFLAGS="%optflags" CXXOPT="%optflags"
-%limit_build -m 1400
+# can't replace limit_build by _constraints file:
+# * asking memoryperjob=3400 -> unsatisfiable i586 workers
+#   (github.com/openSUSE/open-build-service/issues/10167)
+# * asking physicalmemory=13600 -> unsatisfiable ppc64 workers
+%limit_build -m 3400
 make NINJA="ninja %{?_smp_mflags}"
 
 %install