diff --git a/_constraints b/_constraints
index efe0540..3a8b96b 100644
--- a/_constraints
+++ b/_constraints
@@ -5,16 +5,8 @@
     <!-- build uses 20GB in maintenance projects currently 201502 -->
 	<size unit="G">13</size>
     </disk>
+    <memory>
+      <size unit="M">3000</size>
+    </memory>
   </hardware>
-  <overwrite>
-    <conditions>
-      <arch>i586</arch>
-      <arch>x86_64</arch>
-    </conditions>
-    <hardware>
-      <memory>
-        <size unit="M">2500</size>
-      </memory>
-    </hardware>
-  </overwrite>
 </constraints>
diff --git a/opencv.changes b/opencv.changes
index b20dcf6..b7b1bcd 100644
--- a/opencv.changes
+++ b/opencv.changes
@@ -1,3 +1,11 @@
+-------------------------------------------------------------------
+Sun Nov  3 19:50:04 UTC 2019 - Stefan Brüns <stefan.bruens@rwth-aachen.de>
+
+- Limit build parallelism with limit_build, some ARM and PPC workers
+  have a high SMP/memory ratio and run out of memory otherwise.
+- Apply memory constraints (3GB) to all architectures, avoid being
+  scheduled on very weak workers.
+
 -------------------------------------------------------------------
 Sat Oct 12 23:12:21 UTC 2019 - Stefan Brüns <stefan.bruens@rwth-aachen.de>
 
diff --git a/opencv.spec b/opencv.spec
index d03e7b2..428919d 100644
--- a/opencv.spec
+++ b/opencv.spec
@@ -54,6 +54,7 @@ BuildRequires:  libeigen3-devel
 BuildRequires:  libjasper-devel
 BuildRequires:  libjpeg-devel
 BuildRequires:  pkgconfig
+BuildRequires:  memory-constraints
 BuildRequires:  tbb-devel
 BuildRequires:  unzip
 BuildRequires:  pkgconfig(IlmBase)
@@ -177,6 +178,7 @@ cp opencv_contrib-%{version}/LICENSE LICENSE.contrib
 rm -f doc/packaging.txt
 
 %build
+%limit_build -m 1000
 # Dynamic dispatch: https://github.com/opencv/opencv/wiki/CPU-optimizations-build-options
 # x86: disable SSE on 32bit, do not dispatch AVX and later - SSE3
 #      is the highest extension available on any non-64bit x86 CPU