diff --git a/src/clib/pioc.c b/src/clib/pioc.c
index eff9feba4ce..63462c5ff5b 100644
--- a/src/clib/pioc.c
+++ b/src/clib/pioc.c
@@ -693,8 +693,9 @@ int PIOc_init_decomp(int iosysid, int pio_type, int ndims, const int *gdimlen, i
                      const PIO_Offset *compmap, int *ioidp, int rearranger,
                      const PIO_Offset *iostart, const PIO_Offset *iocount)
 {
-    PIO_Offset compmap_1_based[maplen];
+    PIO_Offset *compmap_1_based;
     int *rearrangerp = NULL;
+    int ret;
 
     LOG((1, "PIOc_init_decomp iosysid = %d pio_type = %d ndims = %d maplen = %d",
          iosysid, pio_type, ndims, maplen));
@@ -703,6 +704,10 @@ int PIOc_init_decomp(int iosysid, int pio_type, int ndims, const int *gdimlen, i
     if (rearranger)
         rearrangerp = &rearranger;
 
+    /* Allocate storage for compmap that's one-based. */
+    if (!(compmap_1_based = malloc(sizeof(PIO_Offset) * maplen)))
+        return PIO_ENOMEM;
+
     /* Add 1 to all elements in compmap. */
     for (int e = 0; e < maplen; e++)
     {
@@ -711,8 +716,12 @@ int PIOc_init_decomp(int iosysid, int pio_type, int ndims, const int *gdimlen, i
     }
 
     /* Call the legacy version of the function. */
-    return PIOc_InitDecomp(iosysid, pio_type, ndims, gdimlen, maplen, compmap_1_based,
-                           ioidp, rearrangerp, iostart, iocount);
+    ret = PIOc_InitDecomp(iosysid, pio_type, ndims, gdimlen, maplen, compmap_1_based,
+                          ioidp, rearrangerp, iostart, iocount);
+
+    free(compmap_1_based);
+
+    return ret;
 }
 
 /**
diff --git a/src/clib/pioc_support.c b/src/clib/pioc_support.c
index edbdf5f5f37..ecf52c862a5 100644
--- a/src/clib/pioc_support.c
+++ b/src/clib/pioc_support.c
@@ -1154,7 +1154,10 @@ int PIOc_read_nc_decomp(int iosysid, const char *filename, int *ioidp, MPI_Comm
     /* Now initialize the iodesc on each task for this decomposition. */
     if (!ret)
     {
-        PIO_Offset compmap[task_maplen[my_rank]];
+        PIO_Offset *compmap;
+
+        if (!(compmap = malloc(sizeof(PIO_Offset) * task_maplen[my_rank])))
+            return PIO_ENOMEM;
 
         /* Copy array into PIO_Offset array. Make it 1 based. */
         for (int e = 0; e < task_maplen[my_rank]; e++)
@@ -1163,6 +1166,8 @@ int PIOc_read_nc_decomp(int iosysid, const char *filename, int *ioidp, MPI_Comm
         /* Initialize the decomposition. */
         ret = PIOc_InitDecomp(iosysid, pio_type, ndims, global_dimlen, task_maplen[my_rank],
                               compmap, ioidp, NULL, NULL, NULL);
+
+        free(compmap);
     }
 
     /* Free resources. */
diff --git a/tests/cunit/test_perf2.c b/tests/cunit/test_perf2.c
index 61d3099fca9..e42e4a45b8c 100644
--- a/tests/cunit/test_perf2.c
+++ b/tests/cunit/test_perf2.c
@@ -33,8 +33,8 @@
 #define NDIM3 3
 
 /* The length of our sample data along each dimension. */
-#define X_DIM_LEN 256
-#define Y_DIM_LEN 256
+#define X_DIM_LEN 512
+#define Y_DIM_LEN 512
 #define Z_DIM_LEN 64
 
 /* This is the length of the map for each task. */