diff --git a/src/p_setup.c b/src/p_setup.c
index 585799cba..86e4b2ac6 100644
--- a/src/p_setup.c
+++ b/src/p_setup.c
@@ -2042,7 +2042,7 @@ static boolean P_LoadExtendedSubsectorsAndSegs(UINT8 **data, nodetype_t nodetype
 				UINT16 linenum;
 
 				if (vertexnum >= numvertexes)
-					I_Error("P_LoadExtendedSubsectorsAndSegs: Seg %d in subsector %d has invalid vertex %d!\n", k, m, vertexnum);
+					I_Error("P_LoadExtendedSubsectorsAndSegs: Seg %s in subsector %d has invalid vertex %d!\n", sizeu1(k), m, vertexnum);
 
 				segs[k - 1 + ((m == 0) ? subsectors[i].numlines : 0)].v2 = segs[k].v1 = &vertexes[vertexnum];
 
@@ -2052,7 +2052,7 @@ static boolean P_LoadExtendedSubsectorsAndSegs(UINT8 **data, nodetype_t nodetype
 
 				linenum = READUINT16((*data));
 				if (linenum != 0xFFFF && linenum >= numlines)
-					I_Error("P_LoadExtendedSubsectorsAndSegs: Seg %d in subsector %d has invalid linedef %d!\n", k, m, linenum);
+					I_Error("P_LoadExtendedSubsectorsAndSegs: Seg %s in subsector %d has invalid linedef %d!\n", sizeu1(k), m, linenum);
 				segs[k].glseg = (linenum == 0xFFFF);
 				segs[k].linedef = (linenum == 0xFFFF) ? NULL : &lines[linenum];
 				segs[k].side = READUINT8((*data));
@@ -2067,11 +2067,11 @@ static boolean P_LoadExtendedSubsectorsAndSegs(UINT8 **data, nodetype_t nodetype
 				UINT16 linenum = READUINT16((*data));
 
 				if (v1num >= numvertexes)
-					I_Error("P_LoadExtendedSubsectorsAndSegs: Seg %d in subsector %d has invalid v1 %d!\n", k, m, v1num);
+					I_Error("P_LoadExtendedSubsectorsAndSegs: Seg %s in subsector %d has invalid v1 %d!\n", sizeu1(k), m, v1num);
 				if (v2num >= numvertexes)
-					I_Error("P_LoadExtendedSubsectorsAndSegs: Seg %d in subsector %d has invalid v2 %d!\n", k, m, v2num);
+					I_Error("P_LoadExtendedSubsectorsAndSegs: Seg %s in subsector %d has invalid v2 %d!\n", sizeu1(k), m, v2num);
 				if (linenum >= numlines)
-					I_Error("P_LoadExtendedSubsectorsAndSegs: Seg %d in subsector %d has invalid linedef %d!\n", k, m, linenum);
+					I_Error("P_LoadExtendedSubsectorsAndSegs: Seg %s in subsector %d has invalid linedef %d!\n", sizeu1(k), m, linenum);
 
 				segs[k].v1 = &vertexes[v1num];
 				segs[k].v2 = &vertexes[v2num];