diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 5674e83c9..cb14c83b3 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -74,6 +74,7 @@
 
 #if __linux__
 #include <sys/personality.h>
+#include <sys/mman.h>
 #endif
 
 #if HAVE_STATVFS
@@ -2128,14 +2129,17 @@ void DerivationGoal::startBuilder()
         ProcessOptions options;
         options.allowVfork = false;
         Pid helper = startProcess([&]() {
-            char stack[32 * 1024];
+            size_t stackSize = 1 * 1024 * 1024;
+            char * stack = (char *) mmap(0, stackSize,
+                PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
+            if (!stack) throw SysError("allocating stack");
             int flags = CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWIPC | CLONE_NEWUTS | CLONE_PARENT | SIGCHLD;
             if (!fixedOutput) flags |= CLONE_NEWNET;
-            pid_t child = clone(childEntry, stack + sizeof(stack) - 8, flags, this);
+            pid_t child = clone(childEntry, stack + stackSize, flags, this);
             if (child == -1 && errno == EINVAL)
                 /* Fallback for Linux < 2.13 where CLONE_NEWPID and
                    CLONE_PARENT are not allowed together. */
-                child = clone(childEntry, stack + sizeof(stack) - 8, flags & ~CLONE_NEWPID, this);
+                child = clone(childEntry, stack + stackSize, flags & ~CLONE_NEWPID, this);
             if (child == -1) throw SysError("cloning builder process");
             writeFull(builderOut.writeSide, int2String(child) + "\n");
             _exit(0);