diff --git a/pyedflib/_extensions/c/edflib.c b/pyedflib/_extensions/c/edflib.c
index 1ca9c15..8820bb0 100644
--- a/pyedflib/_extensions/c/edflib.c
+++ b/pyedflib/_extensions/c/edflib.c
@@ -2338,7 +2338,7 @@ static struct edfhdrblock * edflib_check_edf_file(FILE *inputfile, int *edf_erro
     }
 
     p = 0;
-    if(edfhdr->patient[p]=='X')
+    if((edfhdr->patient[p]=='X') && (edfhdr->patient[p+1]==' '))
     {
       edfhdr->plus_patientcode[0] = 0;
       p += 2;
@@ -2549,7 +2549,7 @@ static struct edfhdrblock * edflib_check_edf_file(FILE *inputfile, int *edf_erro
     edfhdr->plus_startdate[11] = 0;
     p += i + 1;
 
-    if(edfhdr->recording[p]=='X')
+    if((edfhdr->recording[p]=='X') && (edfhdr->recording[p+1]==' '))
     {
       edfhdr->plus_admincode[0] = 0;
       p += 2;
@@ -2569,7 +2569,7 @@ static struct edfhdrblock * edflib_check_edf_file(FILE *inputfile, int *edf_erro
       p += i + 1;
     }
 
-    if(edfhdr->recording[p]=='X')
+    if((edfhdr->recording[p]=='X') && (edfhdr->recording[p+1]==' '))
     {
       edfhdr->plus_technician[0] = 0;
       p += 2;
@@ -2589,7 +2589,7 @@ static struct edfhdrblock * edflib_check_edf_file(FILE *inputfile, int *edf_erro
       p += i + 1;
     }
 
-    if(edfhdr->recording[p]=='X')
+    if((edfhdr->recording[p]=='X') && (edfhdr->recording[p+1]==' '))
     {
       edfhdr->plus_equipment[0] = 0;
       p += 2;