diff --git a/kinclude/csr.c b/kinclude/csr.c
index bd8cf2a..bf54fdb 100644
--- a/kinclude/csr.c
+++ b/kinclude/csr.c
@@ -2,14 +2,18 @@
 
 #ifdef TIMECMP_IN_MEMORY
 
+#ifndef TIMECMP_MEM_ADDR
+#error "You set TIMECMP_IN_MEMORY but did not provide a memory addres in TIMECMP_MEM_ADDR!"
+#endif
+
 void write_mtimecmp(unsigned long long int mtimecmp) {
-    unsigned int lower = mtimecmp;
-    unsigned int higher = mtimecmp >> 32;
+    unsigned int lo = mtimecmp;
+    unsigned int hi = mtimecmp >> 32;
     __asm__(
-        "sw %1, 0(%0)\n"
-        "sw %2, 4(%0)" :: 
-        "r"(TIMECMP_MEM_ADDR),
-        "r"(lower), "r"(higher)
+        "li t0, %0\n"
+        "sw %1, 0(t0)\n"
+        "sw %2, 4(t0)" :: 
+        "i"(TIMECMP_MEM_ADDR), "r"(lo), "r"(hi)
     );
 }
 
@@ -32,9 +36,10 @@ void write_mtimecmp(unsigned long long int mtimecmp) {
 unsigned long long int read_time() {
     unsigned int lower, higher;
     __asm__(
-        "csrr %0, 0xC01\n"
-        "csrr %1, 0xC81\n"
+        "csrr %0, %2\n"
+        "csrr %1, %3\n"
         : "=r"(lower), "=r"(higher)
+        : "i"(CSR_TIME), "i"(CSR_TIMEH)
     );
     return (unsigned long long) higher << 32 | lower;
 }