diff --git a/src/dftbp/common/assert.F90 b/src/dftbp/common/assert.F90
index d9684ab861..4907157b35 100644
--- a/src/dftbp/common/assert.F90
+++ b/src/dftbp/common/assert.F90
@@ -23,7 +23,7 @@ module dftbp_common_assert
 
 
   !> Prints assertion error and abort program execution.
-  subroutine assertError(fileName, lineNr)
+  subroutine assertError(fileName, lineNr, message)
 
     !> Name of the file in which the error occurred.
     character(*), intent(in) :: fileName
@@ -31,9 +31,15 @@ subroutine assertError(fileName, lineNr)
     !> Nr. of the line at which the error occurred.
     integer, intent(in) :: lineNr
 
+    !> Additional message for error
+    character(*), intent(in), optional :: message
+
     write(stdout, '(A)') "!!! UNFULLFILLED ASSERTION"
     write(stdout, '(A,A)') "!!! FILE:      ", fileName
     write(stdout, '(A,I0)') "!!! LINE NR.:  ", lineNr
+    if (present(message)) then
+      write(stdout, '(A,A,A)') '!!! MESSAGE:  "', trim(message), '"'
+    end if
     call abortProgram()
 
   end subroutine assertError
diff --git a/src/dftbp/dftbplus/main.F90 b/src/dftbp/dftbplus/main.F90
index c1eac3155b..a2c7fe3bb3 100644
--- a/src/dftbp/dftbplus/main.F90
+++ b/src/dftbp/dftbplus/main.F90
@@ -1161,7 +1161,7 @@ subroutine processGeometry(this, env, iGeoStep, iLatGeoStep, tWriteRestart, tSto
       call buildS(env, this%ints%overlap, this%skOverCont, this%coord, this%nNeighbourSk,&
           & this%neighbourList%iNeighbour, this%species, this%iSparseStart, this%orb)
     case(hamiltonianTypes%xtb)
-      @:ASSERT(allocated(this%tblite))
+      @:ASSERT(allocated(this%tblite), "Compiled without TBLITE included")
       call this%tblite%buildSH0(env, this%species, this%coord, this%nNeighbourSk, &
           & this%neighbourList%iNeighbour, this%img2CentCell, this%iSparseStart, &
           & this%orb, this%H0, this%ints%overlap, this%ints%dipoleBra, this%ints%dipoleKet, &
diff --git a/src/dftbp/include/common.fypp b/src/dftbp/include/common.fypp
index 4a0f497880..1e4f5cfb00 100644
--- a/src/dftbp/include/common.fypp
+++ b/src/dftbp/include/common.fypp
@@ -42,12 +42,17 @@
 #!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
 #! Check a condition if WITH_ASSERT is True and call assertError if condition is False.
-#:def ASSERT(cond)
+#! If an optional text string is included, print this in addition as an error
+#:def ASSERT(cond, msg=None)
   #:if WITH_ASSERT
   if (.not. (${cond}$)) then
     block
       use dftbp_common_assert, only : assertError
+      #:if msg
+        call assertError("${_FILE_}$", ${_LINE_}$, ${msg}$)
+      #:else
       call assertError("${_FILE_}$", ${_LINE_}$)
+      #:endif
     end block
   end if
   #:endif