diff --git a/rust-coreutils.spec b/rust-coreutils.spec
index 0eb252c..19960b2 100644
--- a/rust-coreutils.spec
+++ b/rust-coreutils.spec
@@ -14,6 +14,12 @@
 %global feature_flags feat_acl,feat_os_unix,feat_selinux,uudoc
 %endif
 
+# Peak memory usage is (on x86_64) roughly 4–5 GB in two parallel rustc
+# processes, building the uudoc and coreutils crates. This is OK on the
+# primary-architecture koji builders, but on more severely memory-constrained
+# systems (like some in RISC-V koji) this may cause swapping or memory
+# exhaustion. Setting a conservative memory limit per process helps.
+%global _smp_tasksize_proc 8192
 %ifarch s390x
 # the default setting causes the build to get killed
 %global rustflags_debuginfo 1