diff --git a/Action.c b/Action.c
index 5d774587..a63b30e4 100644
--- a/Action.c
+++ b/Action.c
@@ -174,8 +174,9 @@ static Htop_Reaction actionSetSortColumn(State* st) {
       char* name = NULL;
       if (fields[i] >= LAST_PROCESSFIELD) {
          DynamicColumn* column = Hashtable_get(dynamicColumns, fields[i]);
-         if (column)
-            name = xStrdup(column->caption ? column->caption : column->name);
+         if (!column)
+            continue;
+         name = xStrdup(column->caption ? column->caption : column->name);
       } else {
          name = String_trim(Process_fields[fields[i]].name);
       }
diff --git a/pcp/PCPDynamicColumn.c b/pcp/PCPDynamicColumn.c
index 141978a7..3c4e6797 100644
--- a/pcp/PCPDynamicColumn.c
+++ b/pcp/PCPDynamicColumn.c
@@ -287,6 +287,9 @@ void PCPDynamicColumn_writeField(PCPDynamicColumn* this, const Process* proc, Ri
 int PCPDynamicColumn_compareByKey(const PCPProcess* p1, const PCPProcess* p2, ProcessField key) {
    const PCPDynamicColumn* column = Hashtable_get(p1->super.processList->dynamicColumns, key);
 
+   if (!column)
+      return -1;
+
    size_t metric = column->id;
    unsigned int type = PCPMetric_type(metric);
 
diff --git a/pcp/PCPProcessList.c b/pcp/PCPProcessList.c
index e4f9a5fd..3001d5e8 100644
--- a/pcp/PCPProcessList.c
+++ b/pcp/PCPProcessList.c
@@ -35,7 +35,7 @@ static void PCPProcessList_updateCPUcount(PCPProcessList* this) {
    unsigned int cpus = Platform_getMaxCPU();
    if (cpus == pl->existingCPUs)
       return;
-   if (cpus <= 0)
+   if (cpus == 0)
       cpus = pl->activeCPUs;
    if (cpus <= 1)
       cpus = pl->activeCPUs = 1;
diff --git a/pcp/Platform.c b/pcp/Platform.c
index 97788569..d5a76b55 100644
--- a/pcp/Platform.c
+++ b/pcp/Platform.c
@@ -396,15 +396,15 @@ void Platform_getLoadAverage(double* one, double* five, double* fifteen) {
    }
 }
 
-int Platform_getMaxCPU(void) {
+unsigned int Platform_getMaxCPU(void) {
    if (pcp->ncpu)
       return pcp->ncpu;
 
    pmAtomValue value;
-   if (PCPMetric_values(PCP_HINV_NCPU, &value, 1, PM_TYPE_32) != NULL)
-      pcp->ncpu = value.l;
+   if (PCPMetric_values(PCP_HINV_NCPU, &value, 1, PM_TYPE_U32) != NULL)
+      pcp->ncpu = value.ul;
    else
-      pcp->ncpu = -1;
+      pcp->ncpu = 1;
    return pcp->ncpu;
 }
 
diff --git a/pcp/Platform.h b/pcp/Platform.h
index 9d0c8f53..dcb8dc98 100644
--- a/pcp/Platform.h
+++ b/pcp/Platform.h
@@ -54,7 +54,7 @@ typedef struct Platform_ {
    long long btime;           /* boottime in seconds since the epoch */
    char* release;             /* uname and distro from this context */
    int pidmax;                /* maximum platform process identifier */
-   int ncpu;                  /* maximum processor count configured */
+   unsigned int ncpu;         /* maximum processor count configured */
 } Platform;
 
 extern ProcessField Platform_defaultFields[];
@@ -79,7 +79,7 @@ void Platform_getLoadAverage(double* one, double* five, double* fifteen);
 
 long long Platform_getBootTime(void);
 
-int Platform_getMaxCPU(void);
+unsigned int Platform_getMaxCPU(void);
 
 int Platform_getMaxPid(void);