diff --git a/chunkie/+chnk/+helm2d/transmission_helper.m b/chunkie/+chnk/+helm2d/transmission_helper.m
index 1cc20e5b..cbc6a4e0 100644
--- a/chunkie/+chnk/+helm2d/transmission_helper.m
+++ b/chunkie/+chnk/+helm2d/transmission_helper.m
@@ -124,24 +124,31 @@
         
         c1 = coefs(cs(1,i));
         c2 = coefs(cs(2,i));
-        cc1(1,1) = -alpha1(i)*c1;
-        cc2(1,1) = -alpha1(i)*c2;
-        
-        cc1(1,2) = -alpha1(i);
-        cc2(1,2) = -alpha1(i);
-        
-        cc1(2,1) = alpha2(i);
-        cc2(2,1) = alpha2(i);
+        cc1(1,1) = alpha1(i)*c1;
+        cc1(1,2) = alpha1(i);
+        cc1(2,1) = -alpha2(i);
+        cc1(2,2) = -alpha2(i)/c1;
+
+        cc2(1,1) = alpha1(i)*c2;
+        cc2(1,2) = alpha1(i); 
+        cc2(2,1) = -alpha2(i);
+        cc2(2,2) = -alpha2(i)/c2;
         
-        cc1(2,2) = alpha2(i)/c1;
-        cc2(2,2) = alpha2(i)/c2;
+        % Build the correct system kernel cc1*K_{k1} - cc2*K_{k2}.
+        % Using helmdiff naively with cat(3,cc1,cc2) gives
+        %   cc1*(K_{k1}-K_Lap) - cc2*(K_{k2}-K_Lap)
+        %   = cc1*K_{k1} - cc2*K_{k2} - (cc1-cc2)*K_Lap,
+        % missing the Laplace correction when cc1~=cc2 (i.e. c1~=c2).
+        % Instead use the full Helmholtz 'all' kernel directly.
+        k1_cap = k1(i); k2_cap = k2(i);
+        cc1_cap = cc1; cc2_cap = cc2;
         for j=1:ncurve
-            zks = [k1(i), k2(i)];
-            cc_use = cat(3, -cc1, -cc2);
-            kerns(i,j) = kernel('helmdiff', 'all', zks, cc_use);            
-%            kerns{i,j} = @(s,t) -(chnk.helm2d.kern(k1(i),s,t,'all',cc1)- ...
-%                 chnk.helm2d.kern(k2(i),s,t,'all',cc2));
-        end  
+            kerns(i,j) = kernel();
+            kerns(i,j).eval = @(s,t) chnk.helm2d.kern(k1_cap, s, t, 'all', cc1_cap) - ...
+                                      chnk.helm2d.kern(k2_cap, s, t, 'all', cc2_cap);
+            kerns(i,j).sing = 'log';
+            kerns(i,j).opdims = [2,2];
+        end
     end
     
     
diff --git a/chunkie/@chunker/refine.m b/chunkie/@chunker/refine.m
index 8d9f501d..b9e1c651 100644
--- a/chunkie/@chunker/refine.m
+++ b/chunkie/@chunker/refine.m
@@ -107,7 +107,13 @@
         error('too many chunks')
     end
 
-    chnkr = split(chnkr,ii,[],x,w,u,stype);
+    
+    if max(abs(imag(chnkr.r(:,:,ii))), [], 'all') > 1e-16
+        chnkr = split(chnkr,ii,[],x,w,u,'t');
+    else
+        chnkr = split(chnkr,ii,[],x,w,u,stype);
+    end
+
 
     % update chunklens 
 
@@ -145,7 +151,13 @@
                     error('too many chunks')
                 end
 
-                chnkr = split(chnkr,i,[],x,w,u,stype);
+                
+                if max(abs(imag(chnkr.r(:,:,i))), [], 'all') > 1e-16
+                    chnkr = split(chnkr,i,[],x,w,u,'t');
+                else
+                    chnkr = split(chnkr,i,[],x,w,u,stype);
+                end
+
 
                 % update chunklens 
                 
@@ -215,7 +227,13 @@
                     error('too many chunks')
                 end
 
-                chnkr = split(chnkr,i,[],x,w,u,stype);
+                
+                if max(abs(imag(chnkr.r(:,:,i))), [], 'all') > 1e-16
+                    chnkr = split(chnkr,i,[],x,w,u,'t');
+                else
+                    chnkr = split(chnkr,i,[],x,w,u,stype);
+                end
+
 
                 % update chunklens 
 
@@ -254,7 +272,12 @@
             error('CHUNKER.REFINE nchmax=%d exceeded during oversample',nchmax)
         end
 
-        chnkr = split(chnkr,i,[],x,w,u,stype);
+
+        if max(abs(imag(chnkr.r(:,:,i))), [], 'all') > 1e-16
+            chnkr = split(chnkr,i,[],x,w,u,'t');
+        else
+            chnkr = split(chnkr,i,[],x,w,u,stype);
+        end
 
         % update chunklens 
 
diff --git a/devtools/test/chunkgrphrcipTransmissionTest.m b/devtools/test/chunkgrphrcipTransmissionTest.m
index 04da2442..f9557816 100644
--- a/devtools/test/chunkgrphrcipTransmissionTest.m
+++ b/devtools/test/chunkgrphrcipTransmissionTest.m
@@ -59,7 +59,7 @@ function chunkgrphrcipTransmissionTest0()
 
 nregions = 2;
 ks = [1.1;2.1]*10;
-coefs = [1.0;1.0];
+coefs = [1.1;1.0];
 cs(1,1:ncurve) = 1;
 cs(2,1:ncurve) = 2;
 opts = [];