diff --git a/R/llcont.R b/R/llcont.R
index d8e496a..7463431 100644
--- a/R/llcont.R
+++ b/R/llcont.R
@@ -53,12 +53,16 @@ llcont.glm <- function(x, ...){
              if(is.matrix(y)) {
                ## Bolt: replaced apply(..., 1, sum) with optimized rowSums() for performance
                n <- rowSums(y)
-               y <- ifelse(n == 0, 0, y[, 1]/n)
+               ## Bolt: replaced ifelse with preallocation and vectorized subsetting for performance
+               y <- y[, 1]/n
+               y[n == 0] <- 0
              } else {
                n <- rep.int(1, length(y))
              }
              m <- if (any(n > 1)) n else wt
-             wt <- ifelse(m > 0, (wt/m), 0)
+             ## Bolt: replaced ifelse with preallocation and vectorized subsetting for performance
+             wt <- wt / m
+             wt[m <= 0] <- 0
              dbinom(round(m * y), round(m), mpreds, log = TRUE) * wt
            },
            quasibinomial = {
diff --git a/tests/testthat/test_llcont_glm_binomial_zero_contract.R b/tests/testthat/test_llcont_glm_binomial_zero_contract.R
new file mode 100644
index 0000000..d86af8d
--- /dev/null
+++ b/tests/testthat/test_llcont_glm_binomial_zero_contract.R
@@ -0,0 +1,20 @@
+test_that("glm binomial zero totals and zero prior weights preserve likelihood contributions", {
+  observed <- data.frame(
+    success = c(0, 1, 2, 3, 1, 4, 2),
+    failure = c(0, 4, 3, 2, 4, 1, 3),
+    x = 0:6,
+    prior_weight = c(1, 1, 1, 0, 1, 1, 1)
+  )
+
+  fit <- glm(
+    cbind(success, failure) ~ x,
+    data = observed,
+    family = binomial(),
+    weights = prior_weight
+  )
+  contributions <- llcont(fit)
+
+  expect_true(all(is.finite(contributions)))
+  expect_equal(contributions[c(1, 4)], c(0, 0))
+  expect_equal(sum(contributions), as.numeric(logLik(fit)))
+})