diff --git a/easybuild/easyblocks/a/amber.py b/easybuild/easyblocks/a/amber.py
index 1c77c10696..d646b36b5c 100644
--- a/easybuild/easyblocks/a/amber.py
+++ b/easybuild/easyblocks/a/amber.py
@@ -141,6 +141,17 @@ def configure_step(self):
         if self.toolchain.options.get('openmp', None):
             self.cfg.update('configopts', '-DOPENMP=TRUE')
 
+        # note: for Amber 20, a patch is required to fix the CMake scripts so they're aware of FlexiBLAS:
+        # - cmake/patched-cmake-modules/FindBLASFixed.cmake
+        # - cmake/patched-cmake-modules/FindLAPACKFixed.cmake
+        flexiblas_root = get_software_root('FlexiBLAS')
+        if flexiblas_root:
+            self.cfg.update('configopts', '-DBLA_VENDOR=FlexiBLAS')
+        else:
+            openblas_root = get_software_root('OpenBLAS')
+            if openblas_root:
+                self.cfg.update('configopts', '-DBLA_VENDOR=OpenBLAS')
+
         cudaroot = get_software_root('CUDA')
         if cudaroot:
             self.with_cuda = True
@@ -213,13 +224,14 @@ def configuremake_install_step(self):
 
         # define environment variables for MPI, BLAS/LAPACK & dependencies
         mklroot = get_software_root('imkl')
-        openblasroot = get_software_root('OpenBLAS')
+        flexiblas_root = get_software_root('FlexiBLAS')
+        openblas_root = get_software_root('OpenBLAS')
         if mklroot:
             env.setvar('MKL_HOME', os.getenv('MKLROOT'))
-        elif openblasroot:
+        elif flexiblas_root or openblas_root:
             lapack = os.getenv('LIBLAPACK')
             if lapack is None:
-                raise EasyBuildError("LIBLAPACK (from OpenBLAS) not found in environment.")
+                raise EasyBuildError("$LIBLAPACK for OpenBLAS or FlexiBLAS not defined in build environment!")
             else:
                 env.setvar('GOTO', lapack)