diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
index 8e1422104e..7339c44efd 100644
--- a/docs/man/xl.cfg.5.pod.in
+++ b/docs/man/xl.cfg.5.pod.in
@@ -3083,14 +3083,11 @@ interval of colors (such as "0-4").
 =item B<nr_spis="NR_SPIS">
 
 An optional integer parameter specifying the number of SPIs (Shared
-Peripheral Interrupts) to allocate for the domain. Max is 991 SPIs. If
-the value specified by the `nr_spis` parameter is smaller than the
-number of SPIs calculated by the toolstack based on the devices
-allocated for the domain, or the `nr_spis` parameter is not specified,
-the value calculated by the toolstack will be used for the domain.
-Otherwise, the value specified by the `nr_spis` parameter will be used.
-The number of SPIs should match the highest interrupt ID that will be
-assigned to the domain.
+Peripheral Interrupts) to allocate for the domain. Max is 960 SPIs. If
+the `nr_spis` parameter is not specified, the value calculated by the toolstack
+will be used for the domain. Otherwise, the value specified by the `nr_spis`
+parameter will be used. The number of SPIs should match the highest interrupt
+ID that will be assigned to the domain.
 
 =back
 
diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
index 5a9db5e85f..2d895408ca 100644
--- a/tools/libs/light/libxl_arm.c
+++ b/tools/libs/light/libxl_arm.c
@@ -181,6 +181,12 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
 
     LOG(DEBUG, "Configure the domain");
 
+    if (nr_spis > d_config->b_info.arch_arm.nr_spis) {
+        LOG(ERROR, "Provided nr_spis value is too small (minimum required %u)\n",
+            nr_spis);
+        return ERROR_FAIL;
+    }
+
     config->arch.nr_spis = max(nr_spis, d_config->b_info.arch_arm.nr_spis);
     LOG(DEBUG, " - Allocate %u SPIs", config->arch.nr_spis);